Officials say at around 3:15 p.m., Officer Richard Nicoletti and his partner Matthew McCarthy responded to call at a home on the 1700 block of North 3rd Street.
"They go inside the kitchen, and they see a male seated in the corner with a knife pressed to his throat," Philadelphia Deputy Commissioner Richard Ross said.
Police say say Nicoletti and McCarthy tried for five minutes to calm down the suspect identified by family members as Carmelo Winans.
Winans, who police say was high on drugs, would not let go of the knife, but at one point dropped it.
"Officer Nicoletti tried to charge in to try and save the man's life, actually, in while doing so, he pinned the male's hand down and the male grabbed his gun at that time," Ross said.
Nicoletti's gun discharged once. He called for backup. McCarthy was in the next room, stormed in, and shot Winans twice.
Nicoletti was grazed once in his chest protective gear.
Officers rushed him to Temple University Hospital with police brass and Mayor Nutter soon following.
"We're very fortunate Officer Nicoletti is fine and recovering," Mayor Michael Nutter said.
Nicoletti, 25, is 3-year veteran of the police department.
"He's a tough guy, he's a military vet who served a couple times overseas in Afghanistan, so he's a real tough guy, but it's a chaotic situation when they went in trying to save this male's life and unfortunately, he tried to grab the officer's gun," Ross said.
Winans' family, meanwhile, believes police went too far. They say he didn't deserve to die.
Winans, 29, had recently left a treatment facility, but for what, they wouldn't say.
"They were called for help, they were called to take him to get help. He was supposed to go to Episcopal Hospital for help, that's what he was called for," the suspect's brother Andrew Winans said.
As of Sunday night, Officer Nicoletti is out of the hospital in good condition.
Officer McCarthy is now placed on administrative duty pending an Internal Affairs investigation which is normal protocol.