Sex-Charged Cyberchat Spirals Out of Control

March 18, 2010— -- In the whirl of cyberspace, it was just one chance encounter...

"How r u doing"

"Hey tall, how r u"

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?

It would turn out that all was not quite as it seemed. That good-looking young Marine was actually balding 46-year old Thomas Montgomery, a married father of two. Montgomery said he was stuck in a dead-end job in Buffalo, N.Y., that was "slowly sucking the life out of me." And, he said, he and his wife were drifting apart.

Montgomery began spending a lot of time on the Internet. "I found it easier to talk to the people online than I could to my own wife," he told "20/20."

To this day, Montgomery can't quite explain what he was doing in a teen chat room on the popular game site "Pogo," in May 2005. But when a girl named "Talhotblond" started instant-messaging him, he decided to pretend he was 18 too.

"I kept thinking, well, we're never going to meet. ... I'll just play the game with her," he said.

Before long, the flirtation became a romance.

Talhotblond's instant messages revealed that her real name was Jessi, a softball-playing high school senior from West Virginia. She sent Montgomery photos that lived up to her screen name ... and then some.

"There were some ... very provocative poses," he said.

As they got to know each other, Montgomery asked for other photos: He wanted to see what she looked like at her graduation, or at that baseball game -- and Jessi would send them off to him. But in return, she wanted to see what he looked like too; so he sent her his photo from Marine boot camp.

The picture was 30 years out of date. Montgomery's screen name was Marinesniper, a nostalgic harkening back to the six years he spent in the military as a young man.

Today, he hints darkly of covert ops and dark deeds best unmentioned, but U.S. Marine records obtained by "20/20" show that although he qualified as a sharpshooter, he never trained as a sniper or saw action.

But for Jessi, he invented a younger, stronger, more virile version of himself, called "Tommy." "He was my height, 6 feet tall, had bright red hair," said Montgomery, "big shoulders, muscles and all that."

Cyberchat Consumes 'Marinesniper'

Instant messages recovered from his computer show that the online relationship began to consume Montgomery. He told "20/20" that this relationship "became more real to me than real life."

The feeling seemed to be mutual. Jessi and "Tommy" exchanged gifts, phone calls and love letters.

"I love you always and forever, Tommy," wrote Jessi.

"I have never felt this way," Montgomery responded.

Cyberspace Gets Complicated

In December 2005, the married 46-year old Tom Montgomery found himself proposing to Jessi, an 18-year old girl he had never actually met.

Jessi wrote back, "Yes, I will marry you Tommy.… Won't be long till it's Jessica Blair Montgomery."

Montgomery said he finally realized he was in way over his head. "I was panicking. ...The lies kept getting more and more."

He decided that his 18-year-old alter-ego -- now supposedly stationed in Iraq -- would have to die.

"I was going to kill him off. You know, say he was out on a routine patrol. ... But I couldn't do it," he said.

By that point, Montgomery said the relationship was more than a flirtation. "There was virtual sex going on in there between her and Tommy," he said.

While Montgomery said the virtual sex made him "feel kind of dirty," he was in too deep to sever ties with her.

"If I was smart, I would've just ended it, but it was like a, a drug that I needed every day," he said.

Montgomery seemed to be losing touch with reality. He wrote a note to himself: "On January 2, 2006 Tom Montgomery (46 years old) ceases to exist and is replaced by a 18-year old battle-scarred marine ... He is moving to West Virginia to be with the love of his life."

Online Fantasy World Crashes

Fate finally took a hand. In March 2006, Montgomery told "20/20" one of his daughters was using his computer when Jessi happened to instant message him. Montgomery's wife, alerted by her daughter, found a trove of love letters, photos and mementos from Jessi, including a pair of red panties. She sent Jessi a photo of her family and a letter.

"Let me introduce you to these people," she wrote. "The man in the center is Tom, my husband since 1989. ... He is 46 years old."

Montgomery said Jessi was horrified, and broke off the relationship immediately. "She sends me a text message and says, she hates me ... you should be put in jail for this," he told "20/20."

But Jessi also e-mails one of Montgomery's co-workers, a 22-year-old, good looking, part-time machinist named Brian Barrett, to see if it's really true.

Brian's screen name is "Beefcake" and as he consoled Jessi online, she seemed to find a better fit with him -- and perhaps a way to strike back at the combat Marine who wasn't.

Before long, Jessi was sending Brian her photos and the two had become a cyberitem. Marinesniper became consumed with jealousy -- and he wasn't about to take it lying down.

Marinesniper: Brian will pay in blood.