Prosecutors on Thursday also charged Rhett McKenzie Nelson with attempted murder and two robberies.
The case includes special circumstance allegations of multiple murders, murder by means of discharging a firearm from a motor vehicle and using a handgun in the commission of the crimes.
Nelson is expected in court Thursday afternoon. It was not known if he has an attorney.
Authorities allege Nelson shot Dmitry Koltsov from his vehicle in downtown Los Angeles on Monday, attempted to kill Aleksandr Chudetckii, then fatally shot Deputy Joseph G. Solano. They also say he committed robberies in Long Beach.
Nelson's family says he suffers from mental illness and an opiate addiction.