LOS ANGELES - Los Angeles County sheriff's officials on Sunday displayed photos and a video appearing to show a man holding a gun just before he was fatally shot Saturday by deputies in an incident that has generated debate about police use of force.

Sheriff's officials said at a news conference that the man, Nicholas Robertson, 28, fired six to seven shots into the air on a residential street before walking into a bustling shopping district around 11 a.m. The incident took place in the Los Angeles-area city of Lynwood.

He entered at least one business on the boulevard, "behaving erratically with gun in hand," said Capt. Steve Katz of the sheriff's homicide unit. A video displayed at the news conference showed Robertson on the street appearing to hold the gun as the two deputies arrived.

Katz said "public safety was critical here" because there were people on the street, including some at a gas station that Robertson was walking toward. Robertson at one point pointed the gun in the deputies' direction and ignored their commands to drop the weapon, he said.

The deputies opened fire, and in the video released Saturday, continued to shoot as Robertson was crawling. Authorities said he was continuing to hold the gun at that time. In all, one deputy fired 16 shots and the other fired 17.

"When he collapsed, his arms were underneath him, and the gun was still in his hand. There was never a time when the weapon was not in his possession," Katz said.

Katz estimated that the entire confrontation, from the time officers first ordered Robertson, who was black, to drop the gun until the shooting was over, lasted about 30 seconds. Asked if the officers were white, Katz said no.

A group of civil rights organizations is planning its own news conference and is calling for a meeting with McDonnell.

The activists want the U.S. Department of Justice to investigate the shooting and launch a broader probe into the use of force by the Sheriff's Department.

Katz stressed that the investigation is ongoing. He said Robertson might have had some type of "domestic discord" with his spouse that prompted his actions but did not provide details.

The incident comes amid increasing public scrutiny over police-involved shootings both in the Los Angeles area and nationwide. Over the last two years, the Los Angeles Police Department has dealt with several controversial shootings by officers, including one involving an unarmed homeless man on skid row that was also captured on video. That case is still under investigation.

At the shooting site, more than a dozen people gathered in protest Saturday evening, holding signs and yelling into megaphones, "No more stolen lives!" Helmet-clad deputies formed a line and looked on.

Relatives who saw the video said the shooting seemed unjustified to them. "They shot him," said Tracy Brown, 47, of Lynwood, a relative of the Robertson's wife. "They shot him; as he crawled, they continued to shoot him."

Experts familiar with use-of-force cases said deputies will need to explain why they kept shooting as Robertson was on the ground.

This article contains information from the Associated Press.