A trial has begun for the Winnipeg man accused of shooting a 16-year-old girl with a stolen police gun.

Matthew Wilfred McKay, 24, pleaded not guilty Tuesday to attempted murder and 10 firearm offences in connection with the Oct. 24, 2015 shooting that seriously injured Calli Vanderaa. 

Prosecutors allege McKay and another man, Matthew Andrew Miles, were at a party hosted by the son of an RCMP officer where, as they were leaving, they stole a gun, two loaded magazines, a camera, handcuffs and pepper spray from the officer's van.

The two men rode away on bicycles and sometime later arrived at a Mac's convenience store six kilometres away, Crown attorney Manoja Moorthy told Justice Sheldon Lanchbery.

Vanderaa and another young woman were exiting the store when they "noticed Mr. McKay and Mr. Miles staring at them and making hand gestures that they believed to be gang signs," Moorthy alleged. 

Vanderaa and her friend got into a waiting car, with McKay and Miles in pursuit. When the male driver of the car locked the doors, McKay fired a single shot into the car, striking Vanderaa in the chest, Moorthy told the court.

"Mr. Miles attempted to stop Mr. McKay from firing the gun, but was physically unable to get to him in time," Moorthy said. 

The RCMP officer whose son threw the party reported the theft to city police later that morning, launching a joint investigation.

McKay and Miles were arrested at their homes later that day.

Miles pleaded guilty in September to possession of a restricted weapon, possession of a weapon while prohibited and theft under $5,000. He was sentenced to 42 months in prison.

Moorthy said McKay's trial will come down to three issues: identification of the accused, whether the gun was accidentally fired and intoxication.