Vancouver police are searching for a man who allegedly sucker-punched a stranger in the head and left him bleeding on the sidewalk outside a downtown pub.

Police said the 49-year-old victim was attacked while smoking a cigarette outside Pub 340 on Cambie Street the night of Aug. 31.

The blow knocked him unconscious.

Investigators said nothing preceded the punch except a brief conversation, during which they believe something might have set the suspect off and caused him to lash out. They haven’t revealed what that conversation may have entailed.

“This was a cowardly act by someone with no regard for the consequences of his actions,” Const. Brian Montague said in a statement.

“One punch can have a life-altering outcome for the victim, their family, and the attacker.”

The victim was taken to hospital with a head injury and brain bleed, and was forced to stay there for three weeks. Police said he spent many more weeks recovering at home, but has since made a full recovery.

Investigators are now trying to identify a suspect who was caught on a surveillance camera inside the bar. He’s described as a 5-10 tall Aboriginal man in his 30s with a medium build, light complexion and several tattoos.

He was wearing a black jacket with the word “Headrush” on the back.

The incident was just the latest in an ongoing series of separate “one-punch” attacks committed across the city. There have been at least 11 this year, including three that were fatal.

Police said the only apparent common factor in all the attacks appears to be alcohol.

Anyone with information on the latest attack is asked to contact the Vancouver Police Major Crime Section at 604-717-2541, or Crime Stoppers at 1-800-222-8477 to remain anonymous.