Authorities promised a full investigation Tuesday into why deputies riddled a sport utility vehicle and a Compton (search) neighborhood with 120 bullets after the driver led them on a chase, wounding an unarmed driver and possibly striking a deputy.

"The question is: Did they have to fire as many rounds as they did?" Los Angeles County Sheriff Lee Baca (search) told NBC's "Today."

The driver, identified as 44-year-old Winston Hayes (search), had four gunshot wounds and was hospitalized in stable condition Tuesday morning, the Sheriff's Department said.

A deputy was knocked down and bruised when a bullet struck his protective vest during Monday's confrontation. His identity was not immediately released.

"We're not sure how the deputy was injured but it could be from friendly fire," Baca said Monday.

The sheriff told "Today" that the deputies fired 120 rounds.

Deputies had received a shots-fired call early Monday in a neighborhood of Compton where there has been a rise in gang-related shootings. A white SUV had been identified as being involved, Baca said.

When deputies tried to stop Hayes' white Chevrolet Tahoe, he led them on a 12-minute chase at speeds of up to 35 mph, Baca said. Patrol cars tried to box in the SUV, but it drove onto a lawn and then backed into the street toward three deputies, authorities said.

An amateur videotape captured 10 deputies unleashing a fusillade against the unmoving SUV. The vehicle then rolled slowly forward and struck the back of a patrol car.

Trina Hays, 42, said she threw herself onto her lawn when the shooting erupted 20 feet away.

"This is crazy, really, really crazy," she told the Los Angeles Times. "They didn't have any concern for anybody's life, including their own. That's why their own police officer got hit."

Bullets smashed through windows and hit the walls of at least five homes, the newspaper said.

No weapon was found in Hayes' vehicle but a dozen shell casings were found near the spot where the chase began, Baca said.

Hayes was expected to be booked for investigation of assault with a deadly weapon on a peace officer.

The sheriff said the shooting would be investigated by the department and the county district attorney's office. Investigators will try to determine whether some deputies opened fire because they mistook a colleague's friendly fire for an attacker's.

Hayes told deputies that he had used crack cocaine and had driven around the neighborhood for hours before deputies tried to stop him, Baca said.