Gunshot residue was on the hand, waistband and shirt of an 18-year-old man killed by a St. Louis police officer, authorities said Tuesday.

Police union leaders said the lab test by the Missouri State Highway Patrol dispels claims that Vonderrit Myers didn't shoot at the officer on Oct. 8, initiating a fatal exchange of gunfire. The shooting led to a new wave of protests in St. Louis, two months after a white officer in neighboring Ferguson shot and killed an unarmed black 18-year-old, Michael Brown.

St. Louis Police Officers' Association business manager Jeff Roorda cited other evidence against Myers during a news conference: Social media photos that Roorda said show Myers holding three guns, one of them a 9 mm Smith & Wesson. Roorda said it is likely the stolen gun Myers used to shoot at the officer. He did not provide copies of the photos.

Myers' family contends that he was unarmed and that the officer, who was in uniform but who was off-duty and working for a security company at the time, mistook a sandwich Myers was holding for a gun.

Myers' father, Vonderrit Myers Sr., declined to comment Tuesday. Gerryl Christmas, an attorney for the family, said they want complete investigation, not one conducted in bits and pieces.

"When somebody's son is dead, don't they deserve a full and thorough investigation?" he said.

The shooting set off a new round of intense protests similar to those in Ferguson after Brown's death. Both Brown and Myers were black. Both officers are white. A state grand jury is deciding whether charges will be filed against the Ferguson officer, Darren Wilson. The St. Louis officer has not been named and is on administrative leave while the shooting is investigated.

The officer was working a moonlighting job as a security officer hired to patrol a neighborhood near the Missouri Botanical Garden in south St. Louis. Though not on duty, he was wearing his police uniform and armed with his department-issued gun, which is common practice in St. Louis.

Police Chief Sam Dotson said the officer became suspicious when Myers and the men with him started to run.

A chase ensued and the officer and Myers got into a physical confrontation. After Myers pulled away, Dotson said, he went up a hill and started shooting at the officer.

Ballistic evidence shows Myers fired three shots before his gun jammed, Dotson said. Police said they recovered the gun, which was reported stolen on Sept. 26.

Roorda said the gun in the photo was an exact match for the gun found on Myers after his death.

"This is a distinct-looking gun, not one seen on the streets very often," he said.

Roorda called political leaders who blamed the police for Myers' death "irresponsible and despicable."

"The allegation that the young man had nothing but a sandwich was a silly allegation proven quickly to be untrue," he said.

The officer fired off 17 rounds. Preliminary autopsy results show Myers was struck six or seven times and died from a wound to the head, according to medical examiner Dr. Michael Graham.

Online court documents show that Myers was free on bond when he was killed. He had been charged with the unlawful use of a weapon, a felony, and misdemeanor resisting arrest in June.

The officer's attorney, Brian Millikan, said the shooting was "a traumatic event in his life." He said the officer is undergoing counseling.

Several protests have taken place in the area of the shooting, some that have turned violent, with several police cars damaged. Officers arrested 17 protesters and used pepper spray Sunday after 200 people gathered not far from where Myers was killed. The protesters, some wearing masks, marched toward a QuikTrip convenience store and tried to force open its doors, according to police.