The activists were gathered outside a Marriott hotel in downtown Oakland. Inside, the Urban Shield 2013 conference was taking place — an annual training event for 150 local, state, federal and international law-enforcement agencies, hosted by the Alameda County Sheriff's Department. Friday was a trade show for vendors to promote the latest in law-enforcement technologies, including automatic and semiautomatic weapons, surveillance drones and nonlethal crowd-control weapons. Over the weekend, participants engaged in 54 training scenarios staged in cities throughout the Bay Area.

OAKLAND, Calif. — On Friday morning, a small crowd of activists looked on as Carey Downs, a middle-aged man from nearby Stockton, held up a black-and-white photograph of his son, James Rivera Jr. "On July 22, 2010, my son was shot dead by two Stockton police officers," said Downs as he pointed at the photograph, which showed a young man’s back marked by a bullet wound. "It was the day before his 17th birthday."

Urban Shield was conceived in 2007 by Alameda County Sheriff Gregory Ahern as a way to secure Department of Homeland Security funding for law-enforcement training. Although the event is in its seventh year, this was the first time that it was met with any kind of community protest.

Outside the hotel, the roughly 100 activists assembled to protest what they term the militarization of the police and the history of police brutality in the Bay Area. Many of them blamed conferences like Urban Shield for promoting "war games" in local communities; some held signs that read "Stop the killing of black and brown youth!"

Downs and his wife, Dionne Smith-Downs, drove from Stockton, a few miles northeast of Oakland, to share their story.

"They stopped my son minutes before his death and then let him go," he continued. "Then the officers did what they call a pit maneuver to push the car he was driving into two metal mailboxes and then into the side of a garage. When my son began to back up, they began shooting an AR-15 assault rifle and 9-mm pistols at my son."

Downs and Smith-Downs say that, three years later, they have yet to see an official police report or any accountability for their son’s death. The Stockton Police Department first said Rivera’s car fit the description of a carjacking, then later said they began to shoot because Rivera was backing up his car.

Rivera is one in a long list of casualties of police violence in the Bay Area — the vast majority of whom are black or Hispanic and live in low-income neighborhoods. Just this week, 13-year-old Andy Lopez of Santa Rosa was shot seven times by a Sonoma County Sheriff’s deputy who said he thought Lopez was armed. The gun Lopez was holding was a toy that fires pellets, according to news reports.

"It is sad to be going to so many funerals instead of graduations, and we want to change that," Downs told Al Jazeera.