Justin Carter was 18 when he and a friend got into an argument with someone over a multiple player online video game, leading the teenager to post a comment he now regrets.
He now faces up to eight years in prison after saying 'I'm going to go shoot up a school full of kids and eat their still beating hearts' only two months after the Sandy Hook school massacre.
Arrest: Justin Carter faces up eight years in prison for joking about carrying out a school massacre
Although the teenager, who turned 19 while in prison, added 'lol' (laughing out loud) and 'jk' (just kidding) to his post, a woman from Canada who saw it reported Justin to police after finding out that he lived near an elementary school.
Mr Carter is now campaigning to have his son released, and wants to teach teenagers about the dangers of posting comments on social media.
'Justin was the kind of kid who didn't read the newspaper. He didn't watch television. He wasn't aware of current events. These kids, they don't realize what they're doing. They don't understand the implications. They don't understand public space,' he told KHOU.
His son first got into trouble in February after he and a friend had been playing League of Legends.
Regrets: Justin Carter, who has been in jail since February, wishes he had never posted the sarcastic comment
Game over: Justin had been playing League of Legends when he got into an argument with an online player
He added that his son had made it clear that the comment was made in jest.
A woman in Canada contacted the police after a Google search showed Justin's last known address was close to Wooldridge Elementary School in Austin.
Campaign: Justin's father, Jack Carter, has started an online petition to raise awareness about the case
A spokesman for Austin police said that after recent events statements such as the one Justin made are taken seriously.
The teenager's family have set up an online petition - Release Justin Carter - to raise awareness of his case.