Police reported loud barking could have been a trigger in a mass shooting that left five people and two dogs dead at a Phoenix home on Saturday.

According to CBS News, the five - including four members of a family - were shot by alleged gunman Michael Guzzo, a 56-year-old neighbor to the victims.

Guzzo died after turning the gun on himself, following the shooting rampage.

Phoenix police Sgt. Tommy Thompson said Sunday that there was "some indication that perhaps [barking] was a problem," but added that his team still was unsure of the motive, and may never find out, for all witnesses were killed.

The victims have been identified as 66-year-old Bruce Moore, his daughter Renee, 36, her husband, Michael Moore, 42, and Renee's son, Shannon Moore, who was 17 years old.

Police told CBS affiliate KPHO that Guzzo supposedly shot the family members and dogs, then crossed the courtyard of the complex and shot through a door and window of another townhouse. No residents at the second townhouse were harmed.

Guzzo then left the apartment and returned to his own, police reported, adding that they'd found the pump shotgun which appeared to be the firearm used in the killings, next to his body.

One of Guzzo's neighbors told KSAZ-TV that the deceased man was quiet, and usually kept to himself.

"I've seen him every morning - come in quiet every morning," Donald McKenzie told the Pheonix television station. "Never would expect him to be the guy who did this at all."

Another neighbor named Barry Hatchett told KNXV-TV that he was an acquaintance of Renee Moore's. Hatchett said he was going to take his dog to the Moores' for a grooming session.

Resident of the second townhouse Libni DeLeon told KNXV-TV that there was a knock on the door Saturday morning. As he approached, the gunman shot through the entrance, leaving numerous bullet holes around his house.

"I ran upstairs and when I got there, I got a glance at him, and I yelled at him, and he turned around and shot two more rounds upstairs," DeLeon reported.