Smith shot himself in front of police officers last week after they tried to question him about the publicist's murder.
Chasen was shot to death in her Mercedes-Benz on Nov. 16 while driving home from a movie premiere.
Investigators believe Smith rode his bicycle to Beverly Hills the night of Chasen's murder and waited at a dark intersection of Sunset Boulevard and may have attempted to rob the 64-year-old publicist.
"We believe that Mr. Smith acted alone. We don't believe it was a professional hit, and I will tell you it's an open and ongoing investigation," said Beverly Hills Police Chief David Snowden.
"This was a random act of violence. With Mr. Smith's background, we believe it was most likely a robbery gone bad," said Sgt. Michael Publicker.
Smith has a long rap sheet. He had been in and out of prison for drug and robbery charges. Police cannot conclusively say what Smith's motive was for killing Chasen, but they said it doesn't appear anything was taken from her car.
A woman who was violently attacked by Smith in 1998 said she feels a sense of relief that he won't harm anyone again.
"I was always scared - I was always thinking someone was following me," said Farah Tehrani, who was held up at knife-point by Smith while she was checking her mail box at her Beverly Hills home.
Just hours earlier police said Smith had attacked another woman, laid her on the ground and kicked her in the head, breaking her jaw.
Tehrani's testimony helped put Smith behind bars for 12 years but she could never rest easily knowing he would be out on the street again so she moved her family, fearing he would strike again.
But for some people, none of this adds up. Smith's neighbors said he openly bragged that he'd been paid $10,000 to kill Chasen. Others said Smith was a nice guy and couldn't have committed such a crime.
"It doesn't add up to me. I saw this guy every day, he shook my hand, gave me a hug, and he was cool," said Robin Lyle of Hollywood.
"The absurdity of it is mind-boggling. It's almost too frightening to think the other and too stupid to think this, that it was just a man on a bicycle?" said Carol Connors, one of Chasen's friends.
The gun used in the shooting was a .38 caliber revolver, one known for fast discharge. But a firearms expert said it would have taken an experienced marksman to hit Chasen five times in the chest from outside her vehicle.
"In a real life shooting - getting center of mass - that would be hard to do for someone who doesn't shoot on a regular basis," said Greg Block, a certified firearms instructor for law enforcement.
He said if Smith had leaned all the way into the car and shot her at point blank range he may have been able to more easily make the shot.
Yet there are bigger questions for Beverly Hills investigators - even if ballistics tie Smith's gun to the murder of Ronni Chasen, it's not clear he didn't just find the gun after someone else shot her.
"He could have been a hundred yards away, saw someone else shoot her then put it in the gutter in the streets as they take off and he retrieves it. So we have to place him at the scene," said Block.
At Wednesday's news conference, investigators said they still had to examine the bicycle Smith used to get around to look for gun powder residue. If he was able to get very close to Chasen's car, he might have left prints on the door handle. If he never leaned into or touched the car, investigators will have a hard time placing him at the crime.
"It is the perfect crime if he gets away with it. None of this makes sense from an ex-con who has served time. None of this makes sense," said Block.