(CNN) -- Syreeta Myers knows what it is to lose her only child. "It's the worst pain ever." "My life is empty now. My heart is empty."
More than half a dozen bullets struck Vonderrit Deondre Myers, 18, in an encounter with an off-duty police officer. All but one of the shots were nonlethal, striking his lower extremities. The lethal shot hit him in the head.
Myers' mother, Syreeta, doesn't believe her son did anything wrong and blames police. "They took him away from me," she told CNN's Jason Carroll on Friday. "He was just getting something to eat."
But police said Myers shot first, firing three times at the man in a police uniform, who was working on a private security patrol in a neighborhood. The officer returned fire with 17 rounds.
It started when Myers and two other males ran from the officer, who was in a car, St. Louis police said. The off-duty officer pursued them because he thought one of them had a handgun. He tussled with Myers, who pulled a weapon, police said.
After the exchange of fire, Myers was pronounced dead on the scene.
A 9 mm weapon was recovered -- the gun Myers fired with, police said. It was jammed, they said, no longer readily able to fire. The gun had been reported stolen in late September.
Investigators recovered bullets that had flown in the officer's direction. One was lodged in a car, police said Friday.
Protesters invoke Michael Brown
Myers and Brown were both 18, African-American and killed by white police officers. One big difference: Police said Brown was unarmed.
Chants of "no justice, no peace" rang into the night as crowds rallied after the Wednesday evening shooting.
One officer suffered minor injuries and two police cruisers were damaged, Jackson said. A handful of arrests were made.
Protesters also burned at least one American flag, CNN affiliate KSDK reported.
"It's a clear case of this young man being gunned down by an insensitive white officer who was off-duty," Akbar Muhammad, who also is a member of a coalition calling for the officer who shot Brown to be prosecuted, told CNN affiliate KTVI.
Police lawyer: Force not excessive
Neil Bruntrager, a lawyer for the St. Louis Police Officers' Association, dismissed accusations that 17 shots were excessive.
"When he uses deadly force, he uses deadly force until the threat is gone," he said on "Erin Burnett OutFront."
Without video of the incident or unbiased witnesses, the police and the public must rely on physical evidence, he said.
Van Jones, a civil rights activist and CNN contributor, said there is a lot of police mistrust after the Brown killing.
"You're seeing a wholesale breakdown of trust," he said.
The officer, a six-year veteran who has not been named, was placed on administrative leave, per standard department procedure. He served two tours of duty with the military in Iraq and was awarded a Bronze Star and a Purple Heart, Bruntrager said.
CNN's Shawn Nottingham contributed to this report.