ALBUQUERQUE, N.M. >> Hundreds of protesters marched past riot police in Albuquerque on Sunday, days after a YouTube video emerged threatening retaliation for a recent deadly police shooting.

The video, which bore the logo of the computer hacking collective Anonymous, warned of a cyberattack on city websites and called for the protest march.

Albuquerque police said their site had been breached early Sunday afternoon and remained down hours later.

Investigators had not uncovered the source of the hack, police spokesman Simon Drobik said.

“We can confirm that the website disruption is due to a cyberattack,” he said. The site was not “connected to any critical services” and IT personnel are working on the problem, Drobik said.

The demonstrators, meanwhile, arrived at Civic Plaza holding signs protesting recent police shootings, and activists called on various city officials to resign.

The protest began Sunday afternoon and continued into the early evening as demonstrators marched around the city.

By about 6 p.m. Mountain time, a few hundred demonstrators had gathered downtown near police headquarters where they confronted about three dozen officers in riot gear.

Authorities announced over a loudspeaker that the protest was an unlawful assembly. Demonstrators, meanwhile, chanted, “no justice, no peace!”

Alexander Siderits, 23, said he was protesting because he was “fed up” with how police treat citizens. “It has reached a boiling point,” he said, “and people just can’t take it anymore.”

Albuquerque police have been involved in 37 shootings, 23 of them fatal since 2010. Critics say that’s far too many for a department serving a city of about 555,000.

The U.S. Justice Department has been investigating the department for more than a year, looking into complaints of civil rights violations and allegations of excessive use of force.

Last week, Albuquerque police fatally shot a man at a public housing complex. Authorities said he shot at officers before they returned fire.

In the shooting on March 16 that led to the YouTube posting Tuesday, a homeless man was killed in the foothills of the Sandia Mountains on the east side of Albuquerque. The shooting was captured on video and followed a long standoff.

Anonymous, a loosely organized worldwide hacking group, has been blamed for breaking into confidential information and defacing websites.

The FBI has opened an investigation into the shooting.