Anonymous, the computer hacking activist group, uploaded a YouTube video threatening the Hawthorne Police Department for shooting and killing a dog in a widely publicized incident.

The City of Hawthorne's site has been crippled since Monday after a video of the shooting went viral and they were besieged with threats via e-mail and social media.

"We are not sure who is responsible, but there was a DDOS, or distributed denial of service, attack," a police source told the LA Daily News on the condition of anonymity. "The city website has been down since Monday. The city is working with the Web host to get the site back up."

Distributed denial of service attacks is one of Anonymous's favorite tactics. In the past, they've targeted major corporations and individuals including South Pasadena resident and anti-cursing crusader McKay Hatch.

In the video, uploaded on Wednesday, a man wearing the group's usual V for Vendetta mask reads from a prepared statement, calling the shooting of the Rottweiler "unacceptable."

"Police of Hawthorne you must know that you are our primary target," the Anonymous activist says. "This matter will not remain unresolved... We do not forgive, we do not forget. Expect us."

The disturbing video of an officer shooting the dog that belonged to Leon Rosby has been viewed more than 3.8 million times since it was uploaded to YouTube on Sunday. Anonymous is not alone in threatening the Hawthorne police: The officers involved—whose names have not been released— have been the target of numerous death threats, as have their families.

Petitions at change.org, causes.com and whitehouse.gov have gotten more than 130,000 signatures of people calling for the officer who killed the dog to be fired.

The Hawthorne Police Department has launched two investigations into the incident: one into Rosby's alleged interference with a police investigation, and the other is an internal affairs investigation focused on the officers' actions.

An officer's name, badge number and address have been leaked to the Internet, which has only heightened concerns about safety, officials told the Daily News.

Rosby held a press conference Wednesday asking the public to "calm down" and stop making threats against the officers.

UPDATE, 11:30 A.M.: Anonymous also targeted the Fullerton police department after the 2011 beating death of homeless man Kelly Thomas.

Related:

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Hawthorne Police Launch 2 Investigations Into Fatal Dog Shooting

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