Rafael "Pito" Rivera, 32, was shot and killed by Buffalo Police Officer Elnur Karadzhaev on September 12.

Now his family is suing both the Buffalo Police Department and the city, seeking damages for his death and calling the department and city’s response “negligent, careless, and reckless.”

Steven Cohen, an attorney at HoganWillig PLLC, is representing Rivera’s mother, Denice Rivera and filed the notice of claim on Monday.

"It gives them an opportunity to settle the claim, and assuming that they won't, within the next few months, we'll be commencing a lawsuit," Cohen said.

Buffalo police said Rivera had a gun in his hand and ignored commands to drop the weapon.

He then allegedly took off and there was a short foot chase.

Police don't believe Rivera fired his weapon, but they said it was still a situation they believed prompted deadly force.

Cohen, meanwhile, said video shows Rivera was shot in the back while running from police.

"It is deeply, deeply disturbing, and almost as disturbing as the tragic loss of life is the city's position that it's defending its actions and saying this is exactly what we want to do when someone is running away from police when we think they have a firearm," Cohen said.

He adds that the video from a nearby building also does not definitively show that Rivera had a weapon.

The Erie County District Attorney's Office says its investigation into the incident is ongoing.

A request for comment submitted to both the police department and the mayor’s office was not immediately returned.