With scores of protestors expected to converge on Wall Street today to protest the police shooting of Sean Bell, a Brooklyn father who has become a fixture at such rallies will assume a familiar stance: holding a photograph of his son, who was killed by police in California days before Bell was shot.

James Canley, whose 25-year-old son Adrian was shot on November 14 in Thousand Oaks, Calif., has memorialized his son this way for the past month, protesting his death and the shooting of Bell, killed by police on November 25.

“I buried my son, I’m not going to allow them to bury this,” he said yesterday near his Midtown Manhattan office. Today’s noontime demonstration, organized by the December 12th Movement, is being billed as a “Day of Outrage” designed to “shut down Wall Street,” according to a flier for the event.

Dressed yesterday in a suit and tie, Mr. Canley said his son’s death and Bell’s thrust him into political activism. The 50-year-old California native, who moved to Brooklyn in 2003 to work as a salesman for a government agency he declined to identify, is a deacon of his church who visits his family on the West Coast every three weeks. He was in a taxi on his way home from the airport on November 25 when he heard that Bell had been shot by police. Immediately, he thought of his son. “This is the new trend,” he said he thought.

Adrian Canley was shot and killed by police in the parking lot of an apartment complex after an exchange with a plainclothes detective from the Ventura County Sheriff’s Department. According to police there, Canley attempted to run over the detective with his pickup truck, prompting the officer to shoot. A loaded handgun was later found in Canley’s waistband, police said. Mr. Canley contends the gun did not belong to his son.

In the initial aftermath of Bell’s death, Mr. Canley said he left work several times to visit memorials to Bell and to protest the shooting. “I knew what the family was going through,” he said of Bell’s relatives, whom he has seen but never met. “I know the cycle they are going to go through: disbelief, anger, mourning the loss of their son,” he said. With his family in California, Mr. Canley has grieved for his son amid the ranks of police critics here. Several weeks ago, he was interviewed on the Reverend Al Sharpton’s radio show, where he discussed a “national problem” of police aggression and institutional racism. “The demonstrations, to me, give you a little satisfaction, but I know a lot more needs to take place,” he said.

Calling for changes in police policies nationwide, Mr. Canley said he worries about his other children, a 30-year-old daughter and 23-year-old son. But he stopped short of condemning police across the board, and he rejected rhetoric employed by those calling for retaliation against police.”I can understand their frustration, but I don’t believe what they believe,” he said. “I don’t believe all police are bad. I don’t believe everybody’s a racist.”

Despite the accounts of California police, Mr. Canley said he believes his son was mistakenly identified as a gang member because he was biracial and shaved his head. For several weeks before he was shot, Mr. Canley said his son was harassed by police and pulled over for minor traffic violations. Mr. Canley said he believes police hoped to eventually catch his son committing a more serious offense.

Responding to the allegations yesterday, a spokesman for the Ventura County Sheriff’s Department, Captain Ron Nelson, declined to comment on charges that officers followed Canley. “Every officer-involved shooting is a tragic event,” Mr. Nelson said. “We hope to answer all questions when the investigation is completed.”

Pending that determination — which could take several months — Mr. Canley plans to rejoin his family this weekend in California for the first time since he buried his son. They are planning a rally critical of Ventura County police on January 15.

Before that, another demonstration for Bell today: “I will leave my office to go protest in a suit because I want people to see that it’s not bad kids being killed,” he said.