Father mourns toddler killed in Pennsylvania shooting

A father whose one-year-old daughter was among eight people, including children and a pregnant woman, gunned down by a grandfather at a Pennsylvania home, has vowed to remain "strong" for his community.

Julius Windham visited the home on Sunday where mourners had left tributes such as candles, flowers and stuffed animals.

Mr Windham was seen wearing a T-shirt with pictures of the victims with the words, "Forever In My Heart".

"Words can't even explain what I'm going through right now,"

he said.

"But I gotta be strong for my community, you know what I'm saying? My family, my daughters, my sons, everybody."

Authorities have not released the name of the 45-year-old gunman who took his own life inside the home.

Eerie Police Chief Rick Lorah said earlier the man was related to seven of the victims, while the eighth was a friend of the pregnant woman.

Police have not made their names public either.

Police decline to discuss motive

Erie is about 190 kilometres north of Pittsburgh.

Speaking outside the home on Sunday, Mr Windham described the gunman as never seeming distressed or out of the ordinary.

"I think that was a front for him," he said.

"Him every day, him smiling and being just, you would think of nothing like that would happen."

Nicole and Debra Eller, whose best friend was among the victims, said they had known the family for more than 30 years. 

Nicole Eller said the shooter "was a good guy, and then he started going downhill with everything".

"They were a lovely family. Who would have thought this would ever happen?" Debra Eller said.

"Oh my gosh, this is so upsetting. This should have never happened to her or the kids or anybody. His grandchildren, his kids, how can you do that?"

At a news conference on Saturday, Erie Mayor Daria Devlin addressed a portion of her remarks directly to the victims' families.

"I am so deeply sorry," she said.

"What happened to you was horrific, and there is nothing that any of us can say today that will make this any easier … Our entire community is with you, we're grieving with you. And we are here to support you."

Mr Lorah declined to discuss motive but suggested mental health could be a factor. 

Two women kill outside home

According to video and audio evidence recovered by investigators, muffled gunshot sounds rung out inside the home just before two distressed women arrived and pounded on the door.

Police said the gunman came out of the house and shot the women before returning inside.

Mr Lorah said investigators would talk to relatives and examine the mobile phones of the two women killed outside the house.

"They knew something was going on at that house," Mr Lorah said. 

"We have to figure out what that is."

Police found the bodies of a five-year-old boy, a one-year-old girl, two more women, two young men and the shooter inside the house.