It seems like every month we turn on the news to another tragic school shooting. Now imagine watching those reports and finding out the killer is your son. That nightmare turned into reality for one mom in Pennsylvania.

It's hard to even grasp the level of guilt and shame you might feel after your own child walks into a classroom and guns down five students.

But for Terri Roberts, her story since that fateful day is one of hope and, surprisingly, even joy.

Charles Carl Roberts, a troubled soul, storms into a one-room Amish schoolhouse and commits an unspeakable evil on October 2, 2006.

"It's not something a mother can comprehend," said Terri Roberts, Charles's mother.

Terri has stage 4 inflammatory breast cancer -- her doctor optimistically gives her a few more months. Before she leaves this Earth, Terri has a story she wants to tell about what happened in that school house and the dark days that followed.

It all happened in Strasburg, Pennsylvania, Amish Country. Life there is simple, with no modern conveniences or technology

Despite their lifestyle differences, Terri, her husband Chuck and four boys lived in harmony with the Amish. They were more than neighbors -- they were friends.

Chuck, a retired police officer, would often drive his Amish neighbors around town. Chuck and Terri's oldest son, Charlie, was the milkman.

"Charlie was a wonderful son," said Terri. "Charlie was married, had three children, wonderful wife, beautiful kids that he loved dearly."

But no one, not even his mother, knew that Charlie was tortured by a terrible grudge with God over the death of his first daughter, Elise.

"Elise was born, just born too early, her little heart couldn't, wasn't enough with her lungs to keep her going," said Terri. "She lived for 20 minutes."

Terri believes her son wanted revenge, and in his twisted mind he believed the best way to get back at God was to harm innocent children.

That simmering rage was about to explode.

Police say the 32-year-old father stockpiled a frightening arsenal of weapons: a 9mm semi-automatic pistol, two shotguns, a stun gun, two knives, two cans of gunpowder and 600 rounds of ammunition. He then began to plot his deadly rampage at the little schoolhouse in the cornfield where he often parked his milk truck

Terri says her son got up particularly early on October 2, 2006, so he could take his own children to the bus stop. Then he then went home and wrote four suicide notes.

"Charlie had written notes to his children, one to each of the children, telling them how awesome they were and what a good example they could be to one another," said Terri.

The one to his wife Marie read more like a manifesto than a suicide note.

"One to Marie telling her how wonderful she was, but there was something so dark inside of him that he was angry with God because of the death of their first child," said Terri.

And then at 10:45 on that terrible morning, just after the children's snack, Charlie Roberts stormed into the school house.

Police say he excuses the teacher and 14 young boys in the classroom, methodically boards up the windows, barricades the doors and then binds the 10 girls' legs together with wire.

At 10:58 a.m., while police are trying to talk him out, Charlie orders the girls to line up, face the chalkboard, then unleashes his horror and shoots them one by one.

As cops break down the door, Charlie turns the gun on himself.

Five little girls between the ages 6 to 13 were gone; five others were gravely injured.

The terrible tragedy attracted media from around the world, putting this once peaceful little place under a microscope, and casting a dark shadow of shame over the Roberts family.

Terri and Chuck hung sheets over their windows trying to hide from the world. But the next morning an Amish angel dressed in black named Henry came knocking.

"Henry just kept saying 'Roberts, we love you, we don't hold anything against you. We want you in our community and we forgive, we forgive your son,'" said Terri. "It was so amazing."

And Henry wasn't alone.

The police shut down streets and issued a no-fly zone over the cemetery to give the families privacy.

Pastor Dwight Lefever says the Roberts had a hard time finding an undertaker to bury Charlie. And on the day they were finally able to lay their son to rest, the media swarmed. But from across the cornfields came a human shield of kindness.

"As we arrived that day at the burial site, the Amish came out around the sheds and about 30 to 40 Amish came and surrounded us like a crescent prayer covering, protecting us from the big media cameras out on the street to protect us," said Terri. "The first two parents that came up and greeted us at that funeral were the parents that lost not just one daughter, but two daughters at the hand of our son.

"We were almost in tears, to be truthful," said Terri. "There's an old hymn that people in the church sing called 'We're Standing on Holy Ground,' and that day even though it was a cemetery it felt to us like holy ground."

Ten days after Charlie gunned down those little girls, the Amish woke in the middle of the night and bulldozed their little school, paving the way for a new beginning.

It is the story of passion and forgiveness the Amish asked Terri to write.

"They knew we had a story to tell and they knew this part of the story is one that would touch people's lives," said Terri.

The book is appropriately titled, Forgiven: The Amish School Shooting, a Mother's Love, and a Story of Remarkable Grace.

It chronicles a community's unwavering love, and a mother's struggle to forgive her own son.

"I thought, 'Gee, am I forgiving Charlie? Wow. I'm so angry with him for what he's done. Do I forgive him?'" said Terri. "Then I had to question in my mind, 'Wow, if I didn't forgive him I would have the same hole in my heart that my son had that caused him to do something horrendous.' So yes I have forgiven my son."

This October will mark the 10-year anniversary of what the Amish simply call "The Happening."

Terry knows she may lose her battle with cancer soon, but she hopes her story of forgiveness will live on.

"Forgiveness is incredibly difficult, and yet it is so freeing because it can help us to move forward," said Terri. "And that's what I would encourage anyone with, no matter what your darkest day is."