A beautiful 18-year-old girl meets a handsome Iraq-bound Marine in a chat room. Who would have thought it would lead to a two-year affair, a love triangle and murder? Their story has inspired a Lifetime movie. (handout)

A deadly online love triangle covered by "20/20? in 2010 has inspired a television movie airing on Lifetime this weekend.

In 2005, Thomas Montgomery used the screen name "MarineSniper" to pose as a young, handsome Iraq-bound Marine and chatted online with a woman who went by the screen name "Talhotblond." In reality, Montgomery, of Buffalo, N.Y., was a balding 46-year old married father of two. "Talhotblond" said she was an 18-year-old West Virginia high school softball player.

""I kept thinking, well, we're never going to meet. … I'll just play the game with her," Montgomery told "20/20."

But what began as an Internet flirtation would end in death. Montgomery grew jealous after "Tallhotblond" began an online fling with Montgomery's 22-year-old co-worker, Brian Barrett. In September 2006, Montgomery gunned down Barrett in a parking lot. He was later arrested, pleaded guilty to murder and sentenced to 20 years in prison.

The killing of Barrett wouldn't be the only shocking twist in the case. Read the full story here.

The movie " Talhotblond" airs tomorrow at 8 p.m. on Lifetime and stars Garret Dillahunt as Thomas Montgomery and Laura San Giacomo as his wife. The film also marks "Friends" and "Cougartown" star's Courtney Cox's long-form directorial debut. The film's screenplay is based on the 2009 documentary " talhotblond."