TORONTO -- Plainclothes officers were monitoring patrons of a packed ice cream parlour patio when a gunman mowed down a former biker gang associate, QMI Agency has learned.

And just before he pumped five rounds into John Raposo -- known as Johnnie Maserati, for favouring flashy cars -- a server placed a beer in front of the assassin disguised as a construction worker, a source said.

"He was wearing one of those dust masks when he walked onto the patio, sat down at the table and ordered a beer," the source said.

Anyone puzzled by the masked man's appearance at the Sicilian Sidewalk Cafe around 3:20 p.m. June 18 may have relaxed when the suds were served.

But seconds later the assassin opened fire with a .45-calibre semi-automatic, leaving Raposo, 26, with five wounds and patrons scrambling as chairs, glasses and plates crashed onto the patio sidewalk.

An investigator said no one else was shot, but another man was injured in the melee.

Flare-ups have erupted between rival fans after major soccer games, and officers were present for that day's Italy-Ireland Euro 2012 game.

Three officers were in a Tim Hortons outlet across the street when a passerby alerted them to the shooting, the source said. The officers "first thought the sounds were firecrackers."

But when they saw panicked patrons fleeing, they ran to help Raposo, but he had already died from a head wound.

The gunman, who homicide Det.-Sgt. Terry Browne said witnesses later reported seeing "skulking" around the neighbourhood, had vanished while running north onto streets of tightly packed older homes.

Browne, who said the gunman likely wore a blonde wig, called Raposo's slaying a "very public, intended execution."

Dean Michael Wiwchar, 26, was arrested three days later and appeared in court on a first-degree murder charge.

His lawyer, Christopher Avery, professed Wiwchar's innocence in Raposo's murder and requested a publication ban.

Wiwchar is due back in court July 27.