Community activist Kenneth Mark had just left a pizza parlour in Toronto's Junction neighbourhood when two people snuck up behind him and shot him in the head, police say. (Tony Smyth/CBC)

A Toronto man shot dead by two assailants in the city's west end Tuesday night was almost certainly executed for his anti-gang activism, police say.

Kenneth Mark, 29, was known in the community for chasing away gang members trying to recruit youth and had been shot in the neck with a pellet gun 18 months ago for his efforts, his family said Wednesday.

Mark was on his way to work Tuesday night at about 9:45 when he stopped into a pizza parlour on Dundas Street near Runnymede Road, in the Junction neighbourhood. He left the pizzeria to head to the Wal-Mart outlet where he was a night manager, and put on headphones to listen to music while he walked, police said.

Mark was shot in the neck with a pellet gun last year, but he wasn't seriously injured. (Courtesy Mark family)

Video footage from a security camera shows two men were lying in wait for him in a nearby alley.

"He left the pizza store, he walked northbound on Gilmour Avenue there, he got about 60 feet [18 metres], and the suspects ran up behind him and shot him in the back of the head," Det. Hank Idsinga said. "He had no idea."

Paramedics dispatched to the scene treated Mark, but he was later pronounced dead at hospital.

Toronto police are searching for the two killers, who they say were caught on four security cameras in the area, and hope to make arrests by Thursday night.

Mark's family said he was a hard worker and respected community member who had never run into trouble with the law.

"The young offenders, he was always trying to keep them away, and anybody who tried to come in here and tried to sell drugs or deal with drugs... he was trying to keep them away as much as possible," brother Shawn Mark said.

"The result shows that being on the good side sometimes doesn't pay."

'Everything possible'

Police canvassed the neighbourhood Tuesday night for possible witnesses and will return to knock on doors where no one was home.

"We're urging people that were in the area to come forward," Const. Tony Vella said Wednesday.

"It's a fairly decent, safe neighbourhood, and the residents in the area are concerned. We want to do everything possible to identify who was responsible for the killing."

Nuno Pacheco, who has lived in the Junction for more than 20 years, said he thinks the area is changing.

"When I drive by here I see women of the night picking up men. I see people hanging out the in the alleyways with men," Pacheco said. "I know the area's taking a dive."

Tuesday night's shooting is the 62nd homicide of the year in Toronto, and the 11th in the west-end area that stretches from Dundas Street north to Lawrence Avenue between Keele Street and the Humber River. Police brass stationed 30 additional officers in the district last summer.