Investigators are probing former NFL star Aaron Hernandez's bisexuality as a possible motive for murder.

Hernandez, who was serving a life sentence without the possibility of parole for the murder of Odin Lloyd, a semi-professional football player, last week hung himself in his prison cell.

Lloyd's 2013 murder left many unanswered questions, including a motive. According to Newsweek, law enforcement officials believe Lloyd, who was dating the sister of Hernandez's fiancee, was killed because he knew the football star was bisexual.

One of the three suicide notes Hernandez left behind was to his prison boyfriend. He also wrote notes to his fiancee and his daughter.

“One of the notes left by Hernandez was to his prison boyfriend, who is now on 24/7 suicide watch, multiple law enforcement sources confirm,” Newsweek wrote. “Hernandez's sexuality would, of course, not be relevant save for the fact that an intimate relationship he allegedly had with a male former high school classmate was at the center of the investigation into Lloyd's murder.”