A dozen demonstrators locked arms and chained themselves together in the middle of a busy intersection Friday, and hundreds of others held a vigil and marched through Oakland until about 10 p.m. to protest the death of a man who was shot by Oakland police.

The rally and protest march was held for Demouria Hogg, who was shot by officers last Saturday after they found him unconscious in his car on a freeway off ramp with a handgun on the passenger seat.

The protesters blocked the corner of Lakeshore and Lake Park avenues for two two hours starting at 6:30 p.m. as vigil leaders made speeches, sang songs, read poetry and used a microphone to denounce police violence.

Police cordoned off the block and turned away traffic, but did not make any arrests. Then, shortly after 8 p.m., the crowd began to march down Lakeshore chanting “whose streets? Our streets!” accompanied by raggae music blaring from the back of a truck. The group, flanked by dozens of police officers on motorcycles, made its way along the shores of Lake Merritt, making a full circle before dispersing around 10 p.m. at Lakeshore and Lake Park, where the march had started.

“We have to demonstrate,” said Gerald Smith, 65, of the Oscar Grant Committee. “It's important, but it's not enough. We have to organize. Our enemies are powerful and it's our organization that gives us power.”

Other activists demanded transparency during the Hogg investigation.

“It's important to have visibility around this,” said Brianna Gibson, 23, of the Black Youth Project, one of the organizers of the vigil. “We're here not only to remember the man and his life, but to let the leadership of this city know that they will be held accountable.”

Hogg was found passed out behind the wheel of a BMW on Lake Park and Lakeshore avenues at the end of the off-ramp from Interstate 580 in Oakland. Investigators said a loaded handgun with a 30-round magazine was on the passenger seat.

Officers cordoned off the area and used a loudspeaker to try to awaken Hogg, then fired non-lethal bean bag projectiles at the car in an unsuccessful attempt to break the windows. Police said an officer eventually broke the passenger window with a crowbar, awakening Hogg, who was shot twice after he “abruptly reached over with his hands toward the firearm,” said Steven Betz, the female officer’s lawyer.

A second officer also fired his Taser, Police Chief Sean Whent said. Hogg died at Highland Hospital in Oakland. It was the first fatal shooting by Oakland police in two years.

Relatives of Hogg have questioned the narrative put forth by Whent and Betz, saying Hogg may have been incapacitated by a medical emergency and unable to respond to police.

“I feel like they shot first,” said Teandra Butler, 29, the mother of Hogg’s 8-year-old son. “They should have used other tactics to arrest him.”

The demonstrators issued a list of demands Friday, including the immediate release of the names of the officers who shot Hogg, footage from officers’ cameras or video surveillance and the coroner’s report. The statement also called for the appointment of a special prosecutor from the U.S. Attorney General.

“Police do not have license to shoot people simply for possessing a firearm,” said Cat Brooks, the lead organizer of the Anti-Police Terror Project. “Would Demouria Hogg have been killed for sleeping in his car with a gun on the seat if he were white? It’s difficult to imagine.”

Kale Williams is a San Francisco Chronicle staff writer. E-mail: kwilliams@sfchronicle.com Twitter: @sfkale