Jamel Turner was allegedly driving as fast as 154 mph when he crashed a stolen Camaro in February.
"The crash was so intense that the car exploded," Sini said. "Four individuals burned to death."
The 23-year-old Turner originally faced charges of criminal possession of stolen property and false impersonation. Now he faces second-degree murder charges.
Prosecutors say he was fleeing from police in the stolen car and high on marijuana. The stolen car slammed into a Mazda carrying Jackie McCoy, her daughter Alice Booker, her son Anthony and her son's friend Tameka Foster. They all died, and so did Turner's friend, 19-year-old Lonidell Skinner, who was a passenger in the stolen car.
Donald Mates, Turner's defense lawyer, said the upgraded charges are an overreach.
"It's an accident," he said. "There's no murder here. It's an ill-conceived, over-charged indictment."
Turner has had his license suspended 23 times, and there was a separate warrant out for his arrest at the time of the crash.
"It's my office's intent to ensure that Mr. Turner never, ever gets out of prison," Sini said.
Judge Fernando Camacho ordered Turner remanded with no bail. He's due back in court on May 25.
If convicted, Turner faces life in prison.