Police in Montreal closely watched the funeral service for Nick Rizzuto, the son of the purported head of a top Canadian mob family, and photographed each person who came to pay their respects.

Mourners filled seats in the church, and the turnout was so high that many were forced to stand.

"Everybody was very emotional and very saddened by this day because I think that nobody likes to lose a son," mourner Ricardo Padulo told CTV News.

Nick Rizzuto's casket was brought into the church by pallbearers wearing trench coats. The priest addressed the crowd mostly in Italian.

Rizzuto, 42, was shot in broad daylight by at least one gunman as he stood beside his Mercedes in Montreal on Monday.

Police rushed to the scene and took the victim to hospital, where he was pronounced dead.

His father, Vito, is serving a 10-year prison sentence in Colorado for racketeering related to three mob murders. He is expected to be released in 2012. He had reportedly requested a temporary release from prison in order to attend the funeral, but the request was presumably denied.

The victim's grandfather, Nicolo Rizzuto is out on probation and was on hand to pay his respects. He was arrested in 2006 after police alleged he was part of an organized crime ring that tried to infiltrate Montreal's Trudeau airport to import cocaine.

The family hasn't commented on the murder.

Police at the funeral took photos of each mourner inside the church, in hopes of getting clues as to who committed the crime.

"They take multiple shots and they want to identify every person that is either in another gang, in their gang, or associated with them in legitimate business or in any way connected to organized crime," James Dubro, an author who has written books on the mob, told CTV News Channel.

"The homicide department will also be there looking for possible suspects or people that might have been involved in killing or people who aren't there, noted by their absence," he said.

CTV Montreal's Paul Karwatsky said despite there being a number of witnesses, no one has come forward with a description of the gunman.

Experts fear that the murder could start a gang war in Montreal.

Dubro said the murder shows there is a lack of respect on the street for the old Italian mob, and that its power is waning, while other gangs struggle to become the most powerful in the city.

Dubro said a source he has trusted for 20 years suggested a Haitian gang ordered the hit.

"There isn't another rival gang coming in here to take out the Rizzutos," he said. "It's just sending a message, and the Rizzutos don't have a lot of street people (to defend their status). A lot of them are in jail, some of them are dead, some of them are retired."

Antonio Nicaso, a Canadian journalist who has written books on Canadian and Italian mobsters also said the death of the younger Rizzuto shows a decline in the crime family.

"This is an unprecedented challenge to the Rizzuto crime family. . . Since (the 1970s) they were in charge of criminal activity in Montreal -- without any challenge to their authority," he told The Canadian Press.

Rizzuto was Montreal's 31st homicide of 2009.

With files from CTV's Genevieve Beauchemin and The Canadian Press