BEVERLY HILLS—Hollywood’s mystery about the wealthy publicist gunned down driving home from a movie premiere now appears to be more of a regular crime gone wrong.

Police on Wednesday said preliminary ballistics tests showed the gun a man used to kill himself as officers went to talk to him about Ronni Chasen’s killing was the same weapon that was used to kill her.

Harold Martin Smith, 43, a down-on-his-luck ex-convict with a rap sheet spanning at least 25 years, had apparently ridden his bicycle to a dark intersection on Sunset Boulevard then attempted to rob Chasen.

“This was a random act of violence. With Mr. Smith’s background, we believe that it was most likely a robbery gone bad,” Beverly Hills police Sgt. Mike Publicker said. “Through the interviews and the information we received, that leads us to believe that he was at a desperate point in his life, and was reaching out and doing desperate measures.”

Smith committed suicide Dec. 1 as police, acting on an anonymous tip left with the TV show “America's Most Wanted,” went to speak with him at a seedy Hollywood apartment building from which he had recently been evicted. Before police could talk to him, he pulled out a revolver and shot himself in the head.

It’s another surprising turn in the investigation; just this week, law enforcement sources questioned whether Smith’s gun was even the same kind that was used to shoot Chasen. Neighbors speculated Smith’s boasting about the crime was the ramblings of a man with mental issues who could not have carried out the homicide.

Though police said that gun appeared to be the same one used to kill Chasen, they cautioned that ballistics tests were preliminary and a final analysis could take two weeks.

Smith and Chasen’s lives could hardly have been more different. She left at least a $6 million estate; he had a long criminal record that included two felony strikes — a third conviction could have landed him a lengthy prison sentence. She drove a luxury car; he rode a bicycle. Chasen was well known among Hollywood’s power players and helped actors, directors and composers win Oscars; Smith’s former neighbors recalled him as being mentally unstable.

Police provided no information about who had phoned in the tip that cracked the case but, according to at least one of his former neighbors, Smith had bragged about the killing.