In Colorado, a brother went on a dangerous mission to search for his sister's killer.

Lea Porter was trying to get her life back on track. A former classmate who appeared to be lending her a hand offered her a place to stay.

But that "friend" had a very secret and very dark past.

When Lea went missing, Lea's big brother Maxx went on his own mission to find out what happened to her -- which included confronting the last man to see her alive.

Lea Porter was a despondent 19-year-old who had dropped out of college and broken up with her boyfriend, and left her town of Trinidad, Colorado to move to Denver to make a fresh start.

But instead of finding a new life, Lea meets a horrible death. As police struggle to solve her murder, Lea's avenging older brother Maxx turns detective to try to catch her twisted killer himself.

"I want her found more than anything else in this world," said Maxx Porter. "I would give up my own life to find her right now."

"Getting a confession from Chris is huge. We don't recommend that people go about it that way because it's pretty dangerous to do that, but it was great for the case," said Westminster Police Detective Matt Calhoon.

"That's not how typically we solve criminal cases," said Adams County District Attorney Dave Young. "But that certainly was a factor in solving this one."

"I was so proud of my son," said Rene Jackson, Lea and Maxx's mother.

"There's a really good chance that he'd still be walking around if we didn't do that work," said Maxx.

Christopher Waide will serve to 48 years behind bars after pleading guilty to second-degree murder and sexual exploitation of a child for the images found on his computer.

The Porter family has hired a private investigator who says they've pinpointed four search locations based on the pings from Lea's cellphone. They plan to take a cadaver dog team to those areas with the hope of finding Lea.

To donate to help her family raise money for the search for Lea, visit GoFundMe: Help Find Lea Porter