He told reporters that the man, Mikail Markhasev, had lived in the United States for the past eight years, but that there was no indication that the 16 January killing was connected to any Russian organised-crime group.
Mr Williams said that the murder weapon had been recovered along with a cap after a tip-off from a tabloid newspaper. Forensic tests showed the gun was the one that killed Ennis Cosby.
Mr Cosby, 27, was shot in the early hours of 16 January while changing a tyre on his Mercedes by the side of a freeway.
"It appears that robbery was the motive. It was happenstance," said Mr Williams, who added all indications were that race was not a factor.
The suspect, who is white, was charged with one count of murder, said the police chief.Reuse content