A man called 911 around 10 pm Sunday, saying he had arrived at the complex in a northern Cincinnati suburb to find four members of his family—three women and a man—wounded, according to West Chester Township police.
"They are on the ground and bleeding," said the caller, often choking up and out of breath as the dispatcher struggled to get details from him. "They are all bleeding."
At times, he can be heard on the 911 audio frantically yelling "Help!" apparently to neighbours at the Lakefront at West Chester complex.
Township Police Chief Joel Herzog said at a news conference Monday that it's too early in the investigation to suggest a motive.
It will be up to the Butler County coroner to determine the cause of death and release the victims' identities, Herzog said.
Herzog said that it didn't appear that anyone had shot back at the perpetrator or perpetrators, whom police were still working to identify.
They were also interviewing family members and neighbours.
"It does not appear that the shooter is among the dead," Herzog said, adding that he doesn't believe there is any danger to the community.There was no lockdown in effect at a nearby school, he said.
"It appears to be isolated," Herzog said.
He added that the victims all appeared to have lived in the same apartment in the township, which is a growing, mostly suburban area roughly 20 miles (32 kilometers) north of Cincinnati.
The man who called 911 provided little information on the call about what appeared to have happened. The caller has spoken to investigators, Herzog said. He confirmed that the caller was a relative of the victims.
Police said it appeared the family was preparing dinner when attacked, and there was some smoke when they arrived from the abandoned meal preparation.
Authorities have said that multiple agencies, including the State Highway Patrol, have been assisting in the investigation.
Police established a perimeter around the apartment complex early Monday and used police helicopters and K-9 units to search for a suspect.
Herzog said: "We're actively searching with all the resources we can."