Story highlights Vonderrit Myers, 18, was fatally shot by an officer last week

Police say he fired a pistol three times at the officer

The shooting sparked angry street protests in Missouri

Lab results are back in the case of a teenager who died in a police shooting in St. Louis last week , and they show gun residue on the clothing and body of Vonderrit Myers, authorities said Tuesday.

The residue was found on Myers' shirt, jeans and hand, according to a release from St. Louis police.

Its presence on his hand could mean that he discharged a firearm, was near a firearm when it went off or that Myers touched something with gun residue on it, police said. People shot at close range could also have residue deposited on their hands.

Myers was fatally shot Wednesday by a St. Louis officer, who was off-duty but wearing his uniform while moonlighting for a security company.

Police have said the teenager fired a pistol three times at the officer. Myers' relatives have said they don't believe that account

The shooting sparked street protests, with residents pointing out similarities to the August killing of Michael Brown in nearby Ferguson, Missouri

Myers and Brown were both 18 and black and killed by white police officers. However, unlike Myers, authorities say Brown was not armed.

"We're done as a police union standing in the shadows in these cases. We are actively defending the officer involved in the shooting," Jeff Roorda, business manger of the St. Louis Police Officers Association, told reporters Tuesday.

He said the gun residue results on Myers confirm the officer's account of what happened.

"We saw in the wake of the Michael Brown Ferguson shooting that there was a public outcry, fueled largely by agitators in Ferguson where they demanded that police immediately release details," Roorda said.

"That happened in this case. Police immediately, as information became apparent and known to them, released these facts. ... Even with that, we still saw violence in the street," he said.

Myers was struck by seven or eight bullets, St. Louis Medical Examiner Dr. Michael Graham said last week.

Police say the officer fired his pistol 17 times.

"All but one gunshot wound were to the lower extremities," Graham said. "The one fatal wound was to the head."