A 19-year-old Texan is facing up to eight years in prison after making a sarcastic threat on Facebook.

Justin Carter was arguing about the video game League of Legends when he posted the distasteful Facebook comment.

"I'm f---ed in the head alright, I think I'ma (sic) shoot up a kindergarten and watch the blood of the innocent rain down and eat their still-beating hearts," he said.

Someone reported the comment to authorities, a search warrant was issued and Justin was arrested on February 14 - Valentine's Day. Bond was set at a high $500,000.

"He's very depressed. He's very scared and he's very concerned that he's not going to get out," Justin's father, Jack Carter, told CNN.

Justin could be charged with "making terroristic threats". He is being held in Comal County Jail, near San Antonio, Texas.

Justin's mother, Jennifer Carter, has posted a petition entitled "Release My Son Justin Carter - In Jail For a Facebook Comment" at Change.org.

"My son has been in jail for months because we can't afford to pay the half million dollar bail money," Mrs Carter said.

"Justin's a good kid. He wouldn't hurt anyone, let alone a child."

"The authorities' overreaction is ruining Justin's life. And it's setting a dangerous example trying to punish kids who often say strange things that I believe are protected under freedom of speech."

Jack Carter doesn't begrudge police the right to investigate threats of school violence. Justin's Facebook comment came just two months after 26 people, including 20 children, were murdered by a shooter at Sandy Hook Elementary in Newtown.

But Mr Carter says the need for vigilance doesn't excuse the treatment of his son.

"I definitely see the need to investigate such claims," Mr Carter said.

"But at some point during the investigation there has to be some common sense."

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