Alexandria, Virginia is the type of place where people left their doors unlocked because crime simply didn't happen there. But all that would change in the middle of one autumn day.

Among the million-dollar homes, a killer stalked the streets, picking off members of the city's elite one by one.

Anyone who's ever driven through our nation's capital has experienced the brilliance of Anne Gray Haynes's husband Ronald Kirby.

"He was really smart. He had a Ph.D. in mathematics," Anne tells Crime Watch Daily.

As the city's director of transportation, Ronald Kirby masterminded the construction of the famed Woodrow Wilson Bridge.

He was a genius, no doubt, but to Anne, Ron was simply the handsome love of her life.

"I loved him so much," Anne said.

Anne and Ron bought their dream home in the exclusive neighborhood of Alexandria, Virginia. Only the city's elite could afford to live there. But Ron liked it because it was safe and close to his kids, Joe and Marilyn.

Ron and his first wife had adopted Marilyn and her brother Joe from the Philippines when they were toddlers.

It was the cool fall morning of November 11, 2013. Ron had decided to work from home that day. Anne left for a doctor's appointment, and Ron retreated to his favorite chair in the living room.

"We weren't keeping our doors locked at that time because this is such a nice neighborhood," said Anne.

A short time later there was an unexpected knock at the front door. Little did Ron know that it was a cold-blooded assassin at his doorstep, and Ron was the target.

Three shots fired. The final fatal bullet struck Ron Kirby's heart.

"He shot him here, here, and here, and he had holes in his fingers, and he just fell forward right here," said Anne.

The carpet is now permanently stained with Ron's blood.

"I don't want anybody walking on it. I really don't. I just can't imagine what it was like for him laying there and dying," said Anne.

"Why my dad? What was it that my dad did so bad for someone to take his life away?" said Ronald's daughter Marilyn Kirby. "I wonder the last 10 seconds, two minutes of his life, just all the time, constantly, What was he thinking? Then I felt like, I wish it could have been me."

But before anyone in the family can even begin to grieve the painful loss of Ron Kirby, they find themselves in the line of fire.

"They took me in a police car to the police station and asked me if I had killed Ron," said Anne.

"They started asking 'Would you want to hurt your dad?'" said Marilyn.

There are no strange fingerprints at the scene and no murder weapon. The only odd clue: three silent but deadly subsonic shell casings. It's a rarely used slow-traveling bullet designed to muffle sound when fired. And it apparently worked to perfection.

"Nobody saw anything," said Anne.

Cops were also finding it hard to believe a stranger would walk up to Ron Kirby's front door and open fire in broad daylight, especially in the upscale neighborhood of Alexandria.

"I was trying to figure out like anything I could give, hints or tips or anything they could look at," said Marilyn.

Investigators zero in on a person of interest, and the family is in absolute disbelief.

"[My brother] was the one that found my dad. They usually question the person that finds the victim," said Marilyn. Joe was the one police had questioned the longest.

Joe Kirby was covered in blood when cops arrived at the scene. He told detectives he was supposed to meet his dad for lunch, but found his father on the floor and tried to administer CPR.

Marilyn never believed her brother was capable of killing her father. She wondered if it was someone her dad knew, or maybe someone who carried a grudge against her father. Or could it be some psycho still angry over the building of the Woodrow Wilson Bridge?

For months, the family lived under a dark cloud of suspicion as no other suspects emerged.

A madman was building a legacy of mystery and murder in Alexandria, Virginia.

Before Ron Kirby was brazenly and brutally assassinated in his doorway, there was Nancy Dunning.

"She apparently answered a knock at the front door. Somebody shot her and then immediately left and escaped," said Bryan Porter, Commonwealth's Attorney, Alexandria, Virginia. "Nancy Dunning was very well-known in the community."

Nancy was the beloved wife of Alexandria's own sheriff, James Dunning.

"She was a real estate agent who helped a lot of young families buy their first homes, and took a lot of pride in that," said Porter.

Bryan Porter says Nancy woke up one cold morning in early December 2003. She had plans to meet her husband and son for lunch. Before that, she went out to sneak in a little Christmas shopping. On her way to lunch, Nancy stopped at home to drop off the gifts. Nancy was home all by herself when she heard a knock at the door. When she answered, there was a killer on the other side. Nancy Dunning was executed in cold blood, shot three times.

When Nancy failed to show up for lunch, her son Chris went to check on her.

"Son goes in the house and finds her, immediately calls 911, and it's just a really emotionally wrenching 911 call to listen to," said Porter.

"A few seconds later Jim Dunning arrives," said Bryan Porter. "He comes in the house. And obviously within minutes medics and police officers start to respond.

"No evidence of assault on her person other than the gunshot wounds, nothing disturbed in the home, nothing stolen," said Porter.

Cops initially suspected someone in Nancy Dunning's family pulled the trigger. Jim Dunning was the sheriff at this time. Bryan Porter says at the time there was not anyone else to focus on.

Then, a possible break: cops go back to surveillance video taken at a store showing Nancy shopping earlier that day. It's grainy, but investigators notice a man following Nancy in the store.

"He's a white male, probably in his early 30s. He's got a black leather jacket on," said Porter. "He's got very short close-cropped hair with a prominent widow's peak on the forehead."

The man never grabs a shopping cart. He shadows Nancy from aisle to aisle.

"This man begins to follow her around the store, staying some distance away from her, but kind of tracking her movements throughout the store," said Bryan Porter. "And as soon as she leaves, the same man appears out of nowhere, not having bought anything, and then follows her directly out of the store, maybe three or four feet behind her."

But the video is so grainy cops can't positively identify the man, so they broadcast the surveillance video all around Alexandria, hoping someone will help identify the man.

"That video was released publicly, but it really didn't generate any leads," said Porter.

With no other suspects, Nancy's husband, Sheriff James Dunning, was once again at the center of the investigation. Many people had already convicted him in the court of public opinion.

"There was definitely an air of some suspicion in the community," said Porter.

Sound familiar? When Ron Kirby was shot, cops suspected his family -- specifically his son Joe Kirby. Ron's daughter Marilyn Kirby knew Nancy Dunning's son Chris. They had gone to school together. Marilyn says after her dad was gunned down, Chris contacted her family and gave his condolences.

Do you think there was an instant connection, or did you think it was a separate incident?

"Of course it wasn't 100-percent certain, but then there were like, 'Oh, the M.O. seemed similar, and this could be a serial killer,'" said Marilyn.

Cops were beginning to put the pieces together too.

"There were similarities, and we considered whether Nancy and Ron might be linked, given this method by which the murderers were executed," said Commonwealth's Attorney Bryan Porter.

Nancy Dunning and Ronald Kirby were both highly successful public figures, assassinated when they opened their front doors, and they lived in the same neighborhood that had always been considered extremely safe.

"If you measure, it's about three-quarters of a mile," said Porter.

But the most glaring similarity were shell casings from the same kind of rare bullets, each found at both murder scenes. Yet there was one thing that stumped police.

"There was about a 10-year gap between the first murder and the second murder," said Porter.

Cops know one thing for sure: if they do have a serial killer on their hands, he will eventually strike again.

"The question was how bad of a problem was it, and whether we could stop him before he struck again," said Porter.

Tragically, the answer comes just a few months after Ron Kirby's murder in 2013. It happened on February 6, 2014, when much-loved music teacher Ruthanne Lodato got a knock at her front door.

"There were a total of five rounds fired during this assault. Nothing was stolen, no indication of sexual assault or anything like that. It's just another assassination," said Bryan Porter.

Ruthanne Lodato, the daughter of a prominent judge in Alexandria, was a fixture at her church.

"It was pretty clear that day that we had a serial killer on our hands," said Porter.

Cops determined all three murders have the same modus operandi, the same subsonic bullets, and they all happened just down the street from one other.

"Her and her husband Norm lived about a mile away from the other two victims," said Porter.

But there was one huge difference.

"He believed that Ruthanne was at home alone, but she was not," said Porter. "He's got a witness who is now alive."

Three people had been shot to death in the upscale city of Alexandria, Virginia, and police say all three murders appear to the be the work of the same killer. The only difference at the third crime scene: he left someone alive.

"He definitely engaged in what can only be termed assassinations," said Alexandria, Virginia Commonwealth's Attorney Bryan Porter.

What the assassin didn't know is when he knocked on Ruthanne Lodato's door, she wasn't alone, like his other two victims were.

"A caretaker was also present in the home. And the caretaker heard the commotion," said Porter.

When the caretaker ran to help, the killer took aim at her and fired the last two bullets in the chamber.

"One missed her and one hit her in the arm, but he didn't kill her, and then he fled," said Porter.

But not before the caretaker got a good look at his face.

"A white male in his 50s or early 60s with gray hair and a gray beard," said Porter. "And actually we were able to produce a composite sketch of what he looked like."

And a surveillance camera caught the killer trying to make his getaway two minutes after Ruthanne Lodato was murdered.

"You can see on that video a maroon station wagon traveling away from the general location of the Lodato home, and indeed if you actually freeze frame and look very closely, it appears that there's a white male with a beard driving," said Porter.

The video is too grainy to read the license plate, but cops do notice something unique about the car.

"You can just see this white blob on the back of the bumper," said Porter.

Armed with the sketch and the video of the car, the chief of police held a news conference and pleaded for the public's help.

"The calls just flooded in, much like the D.C. Sniper case. I think in the end they got something like 2,000 tips," said Porter.

One of the calls was a bizarre tip pointing the finger at a former Alexandria mayoral candidate named Charles Severance.

Investigators go back to store surveillance video of the man following Nancy Dunning the day she was murdered. They're stunned. He looks almost identical to Charles Severance. He even appears to be wearing the same black leather jacket he had on in a debate video recorded when Severance was running for mayor of Alexandria.

"The man depicted in the video is definitely consistent with Severance, including the widow's peak," said Bryan Porter.

But neither Severance nor the man in the video looks anything like the most recent police sketch of the suspect. Then police discover a possible link between the former mayoral candidate and the killer's second victim, Ronald Kirby.

"One of his platform planks was that he did not want the Woodrow Wilson Bridge going through the south part of Alexandria," said Porter. "Ron Kirby was instrumental in the Woodrow Wilson Bridge actually being built."

That's enough to send cops to Charles Severance's house.

"This detective left a business card," said Porter. "That detective received an email from Charles Severance's email account, and the email said only, 'I received your business card.' Period. No mention as to whether or not Severance was going to meet with the detective."

But before there's time to follow up with Severance, another peculiar call comes in, this one from the United States Secret Service, saying a bearded man bearing a striking resemblance to their police sketch was caught trying to sneak into the Russian Embassy.

"He tells them that the city of Alexandria is persecuting him and he's seeking asylum," said Porter.

Embassy guards don't hold the man, but before he takes off they snap a picture of his car.

"The car was an exact match of the vehicle depicted on the footage from the surveillance camera on the day of the Lodato murder," said Bryan Porter.

And the car is registered to Charles Severance.

"I think he thought the police were on to him," said Porter.

A few days later police capture Severance on the run in West Virginia. They finally get a closer look at that white blob on the bumper sticker captured earlier on a neighborhood camera.

"I went to the back and there's a circular bumper sticker on the bumper," said Bryan Porter. "It's black and white and it says around it, 'Assassination City Derby.' And in the interior of the sticker is a revolver with five rounds missing from it."

Chilling, because the Alexandria Assassin used a pistol with just five bullets. But it's what they find inside the car that sends shivers down their spines.

"Those are the contents of a green notebook that was recovered from inside of his vehicle," said Porter.

It's now called Severance's "manifesto of hate."

"The real analogy is the Unabomber," said Porter. "He wrote about murdering people, he wrote about his motives for murdering people, he wrote about his obsession with these particular firearms. Things like 'scream of a victim echoes to eternity,' 'subsonic ammunition make sweet, sweet music.'"

Possibly the most disturbing: a self-penned poem to the city's elite, called the "Parable of the Knocker."

"In that parable he writes, 'Knock and the door will be answered.' And then it finishes with really one of the most chilling lines, it says: 'Knock, talk, enter, kill, exit. Murder, murder, wisdom.'"

Also in that green notebook is what prosecutors believe to be his motive for murder.

"One of the writings said 'Can you forgive someone for kidnapping your child, can you murder someone for kidnapping your child? Murder is good,'" said Porter.

Police say Charles Severance was holding a decade-long grudge for the loss of his little boy in a nasty child custody case. And in his twisted mind, murdering the people in power, or their family members, was his only revenge.

So the motive in all of this at the end of the day falls down on that custody dispute all those years earlier.

"The writings absolutely established that," said Porter.

Charles Severance was charged with first-degree murder for the death of Nancy Dunning and two counts of capital murder for the assassinations of Ruthanne Lodato and Ronald Kirby. Prosecutors expect Severance to plead not guilty by reason of insanity.

What mental illness does Mr. Severance have, specifically?

"Schizotypal personality disorder with paranoid features, which shares a lot of components of paranoid schizophrenia," said defense attorney Chris Leibig.

What was the defense's case?

"From the very beginning, the defense was he didn't do it at all," said Leibig.

Despite his terrifying manifesto of murder, Charles Severance's attorneys, Joseph King and Chris Leibig, say cops just got the wrong guy.

Even though he was writing about murders in affluent neighborhoods, you can't directly match that to Alexandria, or to the homes where these happened?

"You cannot," said Leibig.

But how do they explain that bumper sticker, the surveillance tape in 2003, the video of the bearded man and his getaway car leaving Ruthanne Lodato's house moments after her murder?

"There are a number of witnesses that knew Mr. Severance at the time in 2003 that testified at the trial that was not him," said defense attorney Joseph King.

But the most compelling evidence against Severance was the killer's sole survivor, Ruthanne Lodatos's caretaker.

"She was able to point to him and identify him in the courtroom," said Bryan Porter.

And that was enough to find Charles Severance guilty of all three murders.

Does he continue to maintain his innocence?

"I can't answer that," said Leibig.

Commonwealth's Attorney Bryan Porter says even though a sentence of three life terms plus 48 years assures his city is safe from Charles Severance, he still has one heartbreaking regret. Sheriff Jim Dunning, who many suspected murdered his wife Nancy, died before he was vindicated.

"Unfortunately he didn't live to see his name publicly cleared," said Porter.

Was justice served for you and your family?

"It was served in a legal manner," said Ron Kirby's daughter Marilyn. "But at the end of the day it still doesn't bring my dad back, or any of the other family members."

Anne Haynes still lives in the same house, but there is an empty room in her heart.

"My fondest dream is to see him again in Heaven," Anne said.

Charles Severance appealed his conviction, but that appeal was denied.