INGLEWOOD, Calif.  —  A police officer who was videotaped as he slammed a handcuffed teenager onto a car and punched him should be fired and charged with assault, the mayor said Tuesday.

"I will not under any circumstances tolerate the type of conduct I observed in the videotape," Mayor Roosevelt Dorn said at a news conference. Outside, dozens of protesters shouted, "No justice, no peace."

Dorn called for the investigation to finish within 10 days. He said he reached his conclusions after viewing the bystander's videotape, which has been shown repeatedly on national television.

"Based on the investigation he should be fired, no question about it, that's my opinion," the mayor said.

The tape shows Inglewood Officer Jeremy Morse smashing Donovan Jackson, 16, into a car, then striking him in the face during an arrest at a gas station Saturday. Two other officers appear to intervene, with at least one trying to pull away the first officer's arm.

The mayor said the officer's actions were criminal and that he should be charged with assault and violating the teenager's civil rights.

"I'm sure if I looked there are other crimes," Dorn said.

The Inglewood Police Department, the Los Angeles County Sheriff's Department, the district attorney's office and the FBI are conducting investigations.

Morse, who has been with the department for three years, was put on leave with pay Monday. The Police Department referred requests for comment to the police union, which has not returned messages.

The Inglewood officers were assisting two Los Angeles County sheriff's deputies who stopped a car for an expired registration. The car was being driven by Jackson's father, Coby Chavis, 41.

Police and sheriff's officials said the teen lunged at deputies and was combative, while the boy's father said he cooperated and Morse attacked him unprovoked. The family's lawyer, Joe Hopkins, said the teen is developmentally disabled with no arrest record.

The teen was booked for investigation of assault on a peace officer; his father was cited for driving with a suspended license.

The video was recorded by a man who was staying at a motel across the street.

Sheriff's Lt. Carl Deeley said investigators had collected video from gas station surveillance cameras and were attempting to enhance it.

"They are reviewing it and are hopeful that it will give us a different side or angle," he said.

Inglewood, a city of 115,000 in southwestern Los Angeles County, has a police force of 211 uniformed officers.