A 16-year-old San Francisco Bay Area boy has pleaded not guilty to charges that he set a male teen's skirt on fire on a public bus.

Richard Thomas is facing aggravated mayhem and assault charges with hate crime allegations in connection with the Nov. 4 attack.

Authorities say Thomas told investigators he attacked 18-year-old on Luke Fleischman on a bus in Oakland because he was homophobic. Relatives and friends have said Fleischman identifies as "agender," a designation sometimes adopted by people who see themselves as neither male nor female.

Fleischman was sleeping when he was attacked and suffered second and third-degree burns.

The Oakland Tribune reports that Thomas, who has been charged as an adult, entered the plea on Thursday.

His attorney, William Du Bois, says Thomas was playing a prank that went wrong.