Police recalled in detail Wednesday how a gunman killed two young men in a parked sport utility vehicle in downtown Toronto last year, and said a motive for the shootings remains "completely unclear."

Investigators also released a photo of the men that was taken by cellphone just three minutes before Dylan Ellis and Oliver Martin, both 25, were shot.

Martin's girlfriend, who ducked the gunfire from the backseat of the SUV, did not want the photo released, but police said circulating it may help with the investigation.

Police displayed this photo of Oliver Martin, right, and Dylan Ellis, taken on a cellphone just minutes before the men were shot. (Toronto Police Service)

The girlfriend made a "frantic call to 911" after a gunman approached the Range Rover and fired directly into it, killing the two men, Det.-Sgt. Gary Giroux told reporters. The incident took place in front of 798 Richmond St., shortly after midnight on June 13, 2008.

The lack of motive for the shooting is "troubling" and the "most challenging" part of the year-long investigation, Giroux said.

The SUV was parked on Richmond Street at the time of the shooting because the trio only wanted to stop for a brief time to return keys to a friend's condominium in the area.

"Absolutely no one would have known that they were returning to that address, and that's hugely significant to us in our investigation," Giroux said.

"The individuals at the [condo] party, who were long friends since Oliver and Dylan were little boys, were the only ones who would have known that they were going to be returning to the scene," he said.

Giroux said when the "precipitating event" to the murders is determined, he believes it could very well prove to be "hugely insignificant," indicating it was random killing.

While watching an NBA game earlier in the evening, Martin and his girlfriend left the condo to get some food on Queen Street West and took keys to re-enter the gate of the Walnut Avenue condo, a street just off Richmond.

When the pair and Ellis left to return home for the night, they didn't realize they still had the keys until their friends called them as they were approaching Queen and Bathurst streets.

Upon their return to Richmond Street where they had earlier parked, a gunman approached and shot Ellis.

"The windows were down and the music was playing in the vehicle, but not overly loud," Giroux said. "Dylan Ellis looked out the driver side window by turning his head to the left and acknowledged this individual by greeting him with a greeting consistent with 'How's it going?'

"After initial the shots, [the gunman] repositions himself and moves to driver side at the front corner of the SUV and fires again through the window on a diagonal angle," the detective said. "It's this bullet that hits Oliver in the chest."

The pair were pronounced dead after arriving at St. Michael’s Hospital.