Homicide investigators working on the shooting death of Vancouver city worker Hanif Jessa, 53, say they have leads but no suspects, and are appealing to anyone who may have seen the shooting to come forward.

Jessa, who had worked for the city for 25 years, was shot in his vehicle outside his Burnaby home in the middle of the day yesterday, said Sgt. Stephanie Ashton of the Integrated Homicide Investigation Team.

"This investigation has raised concerns throughout the Lower Mainland," said Ashton, who called the killing a targeted attack.

"We want to remind the public that we're treating this homicide investigation with the seriousness it deserves."

Vancouver Mayor Gregor Robertson says the city is 'stunned and saddened' to hear a longtime city employee has been shot and killed. (CBC)

Vancouver Mayor Gregor Robertson expressed his condolences about the killing of a "much-loved" city employee, but offered few details about the nature of the threat that put four city properties under heavy police presence yesterday.

"This is obviously a very disturbing event for city staff," said Robertson at a media briefing Thursday.

"We are obviously stunned and saddened to hear the tragic news of the murder of a longtime city employee."

Jessa had most recently worked as the night supervisor of street cleaning. He was married with two grown sons.

A longtime friend, Hanif Jinnah, said Jessa was an absolute gentleman and will be missed.

"He was very pleasant. Down to earth. Very humble.…Shall I say, kind-hearted? You can't say a bad thing about him," said Jinnah.

"It's tragic to see what has happened here."

No threats prior to shooting

Jessa was shot shortly after noon PT Wednesday on a residential cul-de-sac in Burnaby. He was rushed to hospital, but later died.

Security that had been heightened at numerous locations, including Vancouver City Hall, has now been reduced. (CBC)

By 1 p.m., Burnaby RCMP alerted Vancouver police that there was a potential threat to other people at the city, said Vancouver police Chief Adam Palmer.

The city police sent officers to Vancouver City Hall, the Manitoba and National works yards, and the Crossroads building on West Broadway at Cambie Street.

At about 4 p.m., some city workers were told to evacuate the Crossroads building for the day, but were not told the nature of the threat.

Robertson said the city had not received any threats prior to the shooting, and he deflected questions about whether the shooting had anything to do with city workplace issues.

"I can't speak to the issues with human resources at the city.… There's nothing to suggest that this had anything to do with what happened yesterday."

Flags at Vancouver City Hall are at half-mast following Jessa's death.

Security scaled back

On Thursday morning, Vancouver police announced they were scaling back their presence at city sites.

"As the risk to a City of Vancouver employee has been substantially reduced, the VPD are scaling back resources at work sites," said police spokesman Randy Fincham.

It's not clear what changed to reduce the risk, given investigators said Thursday afternoon no suspects have been arrested.

The Integrated Homicide Investigation Team has taken over the investigation and is working with Burnaby RCMP.