BEVERLY HILLS, Calif. - Investigators said yesterday they believe that a Hollywood publicist was killed by the career criminal who committed suicide last week in a seedy apartment lobby as police closed in on him.

The announcement by Beverly Hills police marks a major break in an investigation that has baffled Hollywood ever since Ronni Chasen was gunned down in her Mercedes last month.

Beverly Hills Police Chief David Snowden said it was a "robbery gone bad," committed by Harold Martin Smith, who has a rap sheet dating back at least 25 years. Snowden also said the gun used by Smith to commit suicide appears to have been used to kill Chasen.

"We believe that Mr. Smith acted alone," he said. "We don't believe it was a professional hit."

Chasen was shot multiple times in the chest Nov. 20 as she drove through Beverly Hills from a premiere of the movie "Burlesque."

Sgt. Mike Publicker said investigators believe that Smith, riding a bicycle, tried to rob Chasen as she waited to turn left off Sunset Boulevard.

"This was a random act of violence," he said. "With Mr. Smith's background, we believe that it was most likely a robbery gone bad at this time.

"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," Publicker said.

Police said that the information leading detectives to Smith was an anonymous tip to "America's Most Wanted" and that that person may be eligible for a $125,000 reward.

Police confirmed that no shell casings had been found at the scene. They did not reveal whether there was any video evidence.

Smith, 43, had been described by police as a "person of interest" after bragging to acquaintances that he killed Chasen.