OAKLAND -- A 16-year-old who told police homophobia caused him to light a sleeping teen's skirt on fire aboard an AC Transit bus Monday night has been charged as an adult and could go to prison for life if convicted, prosecutors announced Thursday.

Richard Thomas, an Oakland High School student, on Thursday was charged with aggravated mayhem and assault with means likely to produce great bodily injury, both felonies that include two hate crime enhancements.

Thomas' "violent and senseless criminal conduct resulted in severe and traumatic injuries to a young and entirely innocent victim," Alameda County District Attorney Nancy O'Malley said.

"The intentional and callous nature of the crime is shocking and will not be tolerated in our community," O'Malley said. "Our thoughts remain with the victim and the victim's family in wishing for a full recovery from the extensive burns suffered as a result of this crime."

Felony aggravated assault carries a maximum prison sentence of life with the possibility of parole, the sentence for the assault charge is a maximum of eight years in prison, and each of the two hate crime enhancements carries one year each in prison, a spokeswoman for the Alameda County district attorney said Thursday.

"During (the) suspect interview, the suspect stated he did it because he was homophobic," lead police investigator Officer Anwawn Jones said in the probable cause statement.

Authorities said Thomas boarded the bus near his high school at 5:20 p.m. Monday, saw 18-year-old Luke "Sasha" Fleischman sleeping in a rear seat and lit Fleischman's skirt on fire. He was arrested at Oakland High School on Tuesday afternoon after bus surveillance footage helped police identify him as the alleged attacker.

Fleischman, a senior at Maybeck High School in Berkeley, suffered second- to third-degree burns and was in stable condition at St. Francis Memorial Hospital's Bothin Burn Center in San Francisco on Thursday.

Friends and family say Fleischman identifies as "nonbinary" gender, meaning the Oakland teen does not identify as male or female. Friends use the pronouns "they," "them" or sometimes "it" when referring to Fleischman, said friend Eve Irwin, 22, of Ben Lomond.

Irwin said she supports authorities moving forward with the harshest punishment possible.

"If you are going to do something that is as close-minded and cruel as lighting someone on fire simply because of what they are wearing, you sort of deserve what you have coming to you," Irwin said.

With his mother, grandmother and a host of other family members looking on, Thomas was arraigned at a courthouse in Oakland on Thursday afternoon. Thomas could not be seen from the gallery, but his grandmother, Juliette Stern, wept as his name was called. They pleaded with the judge to allow more time to hire a lawyer, which was granted.

Family members said Thomas told them he's sorry for what he did and it was a prank or a joke. They denied that Thomas is homophobic.

"He's not a bad person. If you knew him you'd know he's always joking around," his aunt, Juliette Jackson of Oakland said. "He shouldn't have did what he did. I feel so bad. He told me he was scared and he ran when it caught on fire."

Thomas is being held without bail and returns to court Tuesday.

Supporters of Fleischman raised $20,000 in two days to help pay for the 18-year-old's medical bills. More than 400 people chipped in before they stopped the Facebook page collection drive.

Fleischman is expected to undergo massive skin grafting and a weekslong recovery period, the teen's mother, Debbie Fleischman, said.

David DeBolt covers breaking news. Contact him at 510-262-2728. Follow him at Twitter.com/daviddebolt.