Three people have been killed after gunfire erupted in a suburban Philadelphia township, forcing cancellation of a St Patrick’s Day parade and shutting down a children’s theme park, authorities said.

Middletown Township police said there were “confirmed shootings” in the neighbouring Falls Township in Eastern Pennsylvania that resulted in “several gunshot victims”.

Authorities in Bucks County issued a shelter-in-place order for the area, warning residents to stay in their homes and lock their doors.

One local elected official who was briefed by police said characterised the shootings as “domestic”.

Jeffry Dence, chairman of Falls Township board of supervisors, said the suspect went to two locations in the township and shot a number of victims, including three who died.

The suspect then carjacked a vehicle and drove to Trenton, Mr Dence said.

Middletown Township police said a 26-year-old suspect was identified and has ties to addresses in Bucks and Trenton, and while believed to be currently homeless, he “stays in Trenton primarily”.

Shaun Murphy, who lives in the Falls Township community of Levittown, said he was headed to the parade when he saw that the road had been blocked.

Mr Murphy said: “All the neighbours were outside wondering what was going on and then we got the notice about shelter in place.

“I did see ambulances coming up the street earlier without their sirens on,” Murphy said. “My neighbours were just outside with me last night, and we were just saying how great of a town and how great of a neighbourhood it is.”

Pennsylvania state governor Josh Shapiro said in social media posts that he has asked the Pennsylvania State Police to assist local law enforcement agencies.

US representative Brian Fitzpatrick, a Republican who represents Bucks County, said in social media posts that there had been “a carjacking and a shooting in two sections of Falls Township”.

He said he was “in touch with law enforcement officials as they pursue the suspect”.

Police said Oxford Valley Mall and Sesame Place had been told to close until further notice, and the area’s Target store and other businesses chose to close as well.