The NYPD asked the public to tweet a photo of themselves with a member of the department. The idea was to collect photos of officers in their communities with the hashtag #myNYPD.
Instead of posting feel-good photos with police, some posted images of baton-wielding cops arresting protesters, pulling suspects by the hair, unleashing pepper spray and taking down a bloodied 84-year-old man for jaywalking.
"Most of those photos I looked at are old news. They've been out there for a long time. The reality of policing is that oftentimes our activities are lawful but they look awful," said Police Commissioner William Bratton.
The #myNYPD misfire comes at a time when Bratton is trying to re-brand the department to counter criticism that it has been trampling on people's civil rights.
The Twitter backlash is now happening in Los Angeles. The LAPD never asked for it. It never set up a similar plan, but someone came up with #myLAPD and posted pictures showing violent arrests.
"We've been seeing negative things posted on there as well. It's certainly not an official LAPD site, but it's an opportunity for people apparently to vent about how they feel about the police department or to bring up things that people perceive we did wrong in the past," said LAPD Cmdr. Andrew Smith.
The LAPD says it does have several official sites and it gets hundreds of emails a day with similar photos and complaints. Officials say people are welcome to send them whatever they feel. They say it helps to open communications with the public.
"Social media certainly can be your friend and you can use it to get a lot of good exchange of information on there, and other times people can use it to shoot arrows at you. I guess, for a police department, that's OK," said Smith.
The Associated Press contributed to this report.