One person was killed and five injured in separate incidents ahead of the show at the Nokia Theatre L.A. Live, Los Angeles police said. The events were "unauthorized and unaffiliated with the BET Awards," BET said in a statement.
The death and four of the injuries followed gunfire early Sunday at a restaurant, Officer Drake Madison said. Separately, a man was stabbed in the stomach Saturday night at a nightclub.
Rock didn't mention the violence at the show that marks the best in black entertainment. He won over the audience with jokes about Donald Sterling, the hit series "Scandal" and rapper Rick Ross. He called the BET Awards the "black World Cup."
On the red carpet, rapper Nelly said of the violence: "You can't place (the blame) on BET."
R&B singer Ne-Yo had not heard about the incidents until arriving at the show, but he said he doesn't fear for his safety at industry parties and events.
"I feel like the energy I give off is the energy I get back, and I don't give off that kind of energy," he said.
As the show kicked off, a tearful August Alsina, nominated for four honors, won the night's first award for best new artist.
"I represent the struggle," the New Orleans newcomer said onstage. "This award is not for me, it's for the people."
Drake, Beyonce and Jay Z are top nominees with five each. Drake, who was originally set to perform, will not attend, BET said Sunday. A representative for Beyonce also said the singer wouldn't attend, and her husband's rep wouldn't divulge if Jay Z would be there or not. Their attendance had nothing to do with the violence at the weekend parties.
Drake didn't attend last year's show, where he won video of the year. This year, the 27-year-old rapper's "Worst Behavior" is nominated for the top prize, competing with Beyonce's "Drunk in Love" and "Partition," as well as Pharrell's "Happy" and Chris Brown's "Fine China."
Beyonce and Jay Z launched a co-headlining stadium tour days ago. She is nominated for best female R&B/pop artist, with little competition aside from Rihanna, while her husband will battle Drake, Kendrick Lamar, J. Cole and Future for best male hip-hop artist.
Pharrell scored four nominations, including best male R&B/pop artist, best collaboration for Robin Thicke's "Blurred Lines" and the viewer's choice award. Beyonce, Drake, Alsina and Jhene Aiko are also up for the fan-voted award.
Thicke, who is set to release his new album, "Paula" - an ode to his wife, Paula Patton, whom he is separated from - on Tuesday, will perform Sunday. Usher, Mary J. Blige and Iggy Azalea will also take the stage.
Minaj and Azalea - whose anthemic "Fancy" has spent its fifth week on top of the Billboard charts - will compete for best female hip-hop artist, an award Minaj has won consecutively for four years.
Lionel Richie will be honored with a lifetime achievement award at the show, where presenters include Kerry Washington, Kevin Hart and Gabrielle Union.