The Los Angeles County Sheriff's Department is investigating the fatal shooting of an armed man by deputies summoned to the scene after 911 calls reporting he was pointing the weapon at people and firing shots into the air.

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WHAT HAPPENED?

Several alarmed people told 911 dispatchers that they saw a man walking down a street waving a gun and shooting in the air Saturday in Lynwood, a south Los Angeles County city. Video shows deputies shooting at Nicholas Robertson and continuing to fire after the 28-year-old fell and crawled on the pavement. Investigators said two deputies fired more than 30 times after Robertson refused to drop the weapon and walked across a busy street to a filling station where a family was pumping gas.

"There was never a time when the weapon was not in his possession," homicide Capt. Steven Katz said in response to questions about why the deputies kept shooting the man after he was down.

Robertson's family members and some activists said the shooting was not justified and that Robertson may not have heard the deputies' command to drop the gun.

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HOW DOES IT COMPARE TO OTHER POLICE SHOOTINGS MAKING HEADLINES?

The shooting was notably different from some other recent flashpoints in the national debate over police use of force: The suspect clearly had a weapon and was on a busy street full of bystanders and motorists. A family reported he fired the gun in front of their house.

Seth Stoughton, a criminal law professor at the University of South Carolina and a former Tampa, Florida, police officer, said the incident doesn't appear egregious, unlike the killing in his state of Walter Scott, an unarmed man shot in the back by a police officer.

If the suspect wasn't armed or the deputies didn't have a solid basis for the belief that he was armed, that would be more problematic," Stoughton told the Los Angeles Times. More facts, he cautioned, are needed to determine what occurred outside the video.

Robertson's death came less than two weeks after five San Francisco officers shot and killed Mario Woods, 26, after they say he refused commands to drop an 8-inch knife. Police were responding to a stabbing report Dec. 2 when they encountered Woods. Several bystanders recorded video of the shooting.

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HOW HAVE SHERIFF'S OFFICIALS REACTED?

Within a day, authorities released video of Robertson and recordings of the 911 calls that brought deputies to the gas station. A close-up from security footage was released that showed Robertson stretched out on the ground with a gun in his grip.

Los Angeles County Sheriff Jim McDonnell vowed transparency and said the investigation into Robertson's death would be handled "with the utmost professionalism and integrity" and urged anyone with information to come forward.

"There's gonna be criticism anytime there's a deputy-involved shooting. We've seen that in the last two years or so, the sentiment across America has been critical," McDonnell said. "That's why we ... try to be as transparent as we can with the information that we can share."

A multi-agency investigation is planned that will include the Los Angeles County district attorney's office and the sheriff's Homicide Bureau and Internal Affairs Bureau, officials stated in a release.

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WHAT DO USE-OF-FORCE EXPERTS SAY?

Stoughton, the University of South Carolina professor, said there are circumstances under which an officer can shoot at a suspect walking away from them. "If the deputies reasonably believe the suspect with a firearm presents a danger by walking toward a gas station with vehicles and bystanders, they would be justified in using deadly force.

Once the suspect is on the ground, how close the gun is to him is key in whether shots are justified, he said.

Experts familiar with use-of-force cases said deputies will need to explain why they opened fire and continued to shoot as Robertson was on the ground.

"They are going to have to articulate why they made every one of those shots," said Ed Obayashi, an Inyo County deputy and an attorney. "They must show they reasonably used deadly force."