Police reportedly said Oliver, 29, died of a self-inflicted gunshot wound.
Oliver was signed by the Chargers after playing college football at Georgia. He did not appear in a game as a rookie in 2007, but from 2009 to 2011 he played in 45 games, starting in 12, including eight in 2010.
All-Pro tight end
"You just never know; life is so short," Gates said. "My condolences and prayers go out to his family and kids."
Said Rivers: "It's sad to lose anyone, for that matter, but a guy that you played with. ... I can remember interactions with him like it was yesterday."
Wire services and Internet reports contributed to this story.