TORONTO – The family of a U.S. teen is fighting for his freedom after he was jailed for terrorist threats over what his parents describe as sarcastic comments.

18-year-old Justin Carter engaged in an argument on Facebook over the online game “League of Legends” in February when another user started calling him crazy and saying he was “messed up in the head.”

Carter fired back replying, “Oh yeah, I’m real messed up in the head, I’m going to go shoot up a school full of kids and eat their still, beating hearts.”

The next lines the teen typed were “LOL” (laugh out loud) and “JK” (joking).

But an anonymous user from Canada who saw the posts didn’t find it funny.

According to reports, the user used Google to look up Carter’s name and found an address in Texas linked to the teen – that was located near an elementary school – and filed a complaint with local authorities.

Carter was later taken into custody and charged with making a terrorist threat.

Four months later, Carter remains in jail – his parents unable to afford his half a million dollar bond – all for making what his mother described as a “very, very stupid comment on Facebook.”

During a phone interview with Global News, Justin’s mother Jennifer Carter described her son as a typical 18-year-old boy who had never been in trouble before.

She noted that her son has “a dark sense of humor” but that he is a creative boy who likes to write zombie stories, play video games and loves children.

“When I first saw the threat I honestly didn’t take it seriously for a second – he babysits, he hangs out with our friends’ little kids, he likes to teach them how to play video games – he loves kids,” Jennifer Carter told Global News.

“We thought they [the police] would see that he was a teenager being sarcastic on Facebook – but he sat in jail for about a month before he was questioned.”

Though Justin was arrested on February 14 he was not questioned by the police until March 13.

Carter said that during questioning her son admitted to the Facebook posts, acknowledging that what he wrote was wrong and that he was sorry, but enforcing the fact that he wrote the post sarcastically.

A search of Justin’s home was completed by police a week later, but no weapons were found – the only item seized from the teen’s home was his computer.

Jennifer started a petition on the website Change.org asking for her son’s release. She believes that Justin is being held unfairly, claiming that the police have failed to make a case that he is an imminent or likely threat to public safety.

The petition had garnered over 4,000 signatures by Friday afternoon.

“They wanted him to sign for eight years in prison, but he’s refusing to sign because he doesn’t feel that he’s done anything worthy of prison time,” said Carter.

She plans to present the petition to the police once they have gathered enough signatures.

In the mean time Justin’s family continues to fight for his freedom and what they say is a violation of his first amendment right to free speech while he’s in prison.

“Before all of this media attention he was in a pretty hopeless place,” said Carter.

“This has been an eye opener for him – he’s not been treated very well – jail is not a place where you can expect safety.”

Carter said her son has been transferred more than once due to other inmates harassing him and picking on him.

“He’s has a very tough time in jail and I worry about him constantly – I have trouble sleeping at night,” said an audibly distraught Carter.

“It’s just really hard… I understand him having to go through this if he had done something violent or hurt someone… but it’s just something he said on a website.”

The family’s lawyer has suggested that Justin be released on probation with community service to talk to other teens about the dangers of what they say online. The family hopes that by sharing their story they can show other teens that they need to be careful about what they say online.

“I hope that teenagers realize that the stuff they are posting in anger or saying online in a social environment, such as Facebook or Twitter, is being seen by people that don’t know you… don’t understand you sense of humour,” said Carter.

“A lot of teens don’t think about the larger context about what they are saying on social networks.”