Twelve former members of Florida A&M’s university marching band have been charged with manslaughter over the death of a gay student – although the family say it wasn’t a hate crime.

Robert champion, a drum major, was beaten to death in a university bus in 2011 after a game.

Medical officials said Champion died of internal bleeding and had bruises on his chest, arms, shoulder and back.

Witnesses told emergency dispatchers that the drum major was vomiting before he was found unresponsive aboard the bus. He died within an hour, the medical officials said.

There had been speculation that the 26-year-old was disliked by some band members in part because of his sexuality and because of his opposition to hazing – a practice of initiation based on harassment, abuse or humiliation.

In January 2012, during their investigation into what happened to their son, Champion’s family discovered that he was gay, but also concluded that this was not a reason for his alleged hazing.

In the wake of his death, Florida A&M’s marching band was suspended and the university president resigned after a no-confidence vote from trustees.

The manslaughter charges carry a sentence of up to 15 years in prison, if the defendants are convicted.