New York City police officers shot and killed a black man Wednesday after he pointed what they believed was a gun at them, authorities said.
After the shooting, officers discovered the man was holding "a pipe with some sort of knob on it," Chief of Department Terence A. Monahan said at a news conference.
The incident started shortly before 5 p.m., when officers received 911 calls of a man aiming what callers described as a silver firearm at people in Brooklyn, Monahan said.
"Three different 911 callers described a man with a gun, pointing it at people on the streets," he said.
'Two-handed shooting stance'
When officers arrived at the scene, they found a man matching the description provided by the callers, Monahan said.
"The suspect then took a two-handed shooting stance and pointed an object at the approaching officers, two of whom were in uniform," he said.
Four officers discharged their weapons, striking the man, Monahan said. They then gave him first aid and called for an ambulance to take him to the hospital, where he was pronounced dead.
"It appears we fired 10 rounds between the four officers," Monahan said. The unidentified officers, who were not wearing body cameras, discovered the metal pipe at the scene.
'He's polite ... kind'
Brooklyn resident Eric Vassell told CNN affiliate NY1 that the victim was his 35-year-old son, Saheed Vassell.
Saheed Vassell had no access to guns and suffered from bipolar disorder, his father told the station.
"He's polite, nice, he's kind. He just comes and he goes," Eric Vassell said.
Mayor Bill de Blasio said he's received a preliminary briefing on the shooting.
Renewed calls for police reform
The incident comes weeks after Sacramento officers killed an African-American man who they say they believed was pointing a gun at them. A cell phone -- but no weapon -- was found at the scene following Stephon Clark's shooting on March 18.
Clark's killing has sparked weeks of protests and reignited calls for police reform.
In the wake of the shooting, California lawmakers proposed a drastic change that would limit the scenarios in which police officers can use deadly force. The bill would replace the "reasonable force" rule with a stricter "necessary force" standard.
The proposal also would establish that a homicide by an officer is "not justified if the officer's gross negligence contributed to making the force 'necessary,'" according to the proposal.