The surveillance footage from a local business shows 18-year-old Carnell Snell Jr. with a gun in his left hand during a foot chase with police on Saturday afternoon.
Snell's encounter with police started shortly before 1 p.m. Saturday, when officers tried to pull over a car with paper license plates, police said. Officers believed the car was stolen because "the paper plates didn't match the year of the vehicle," Beck said.
But the car didn't stop, and officers gave chase, police said.
When the car finally did slow down, a man later identified as Snell ran out from the back seat, "holding his waistband as if he was supporting something," Beck said.
Officers chased Snell for a few hundred yards, during which time they saw him remove a gun from his waistband, the chief said.
Snell then "turned in the direction of the pursuing officers," Beck said. Police shot at Snell six times, striking him twice.
Snell's mother, Monique Morgan, was visibly distraught as she told reporters her son was shot multiple times.
"My daughter got a phone call," she said as she wept. "It said that the police shot him."
Beck said a semi-automatic handgun found next to Snell's body was fully loaded.
Snell's death was the first of two officer-involved fatal shooting in Los Angeles over the weekend.
On Sunday afternoon officers responded to a report of a man armed with a gun near Ascot Elementary School.
"As the officers approached the male to initiate a pedestrian stop, the male turned and pointed a handgun at the officers," Beck said.
That's when police shot and killed the man. He later died at a nearby hospital.
But when officers examined what looked like the man's gun, they learned it was a "replica handgun -- it is not an actual firearm," Beck said.
He said the orange safety tip, which distinguishes fake guns from real guns, had been blacked out with paint or a black marker "to conceal the fact that it was a replica."
The police chief said he has reviewed body camera footage of the shooting, which he said supports the officers' accounts of what happened.
Beck said authorities have not been able to identify the man shot Sunday, described as a Hispanic male wearing a gray sweater and black pants. He asked anyone who might know the man's identity to call police.
As with any officer-involved shooting, LAPD's Force Investigation Division will investigate and present its findings to Beck. The chief, along with the LAPD board of commissioners, will determine whether officers complied with department procedures.
The Los Angeles District Attorney's Office also plans to investigate.
The incidents follow recent police-involved shootings in El Cajon, California;
Tulsa, Oklahoma; and Charlotte, North Carolina
. The shooting victims in El Cajon and Tulsa were unarmed,
but questions remain on whether the victim in Charlotte had a weapon.