A man faces murder charges in Pennsylvania and carjacking and weapons charges in New Jersey after allegedly killing three family members, carjacking vehicles in both states and evading police for hours, authorities said.

Andre Gordon Jr, 26, is charged in Bucks County, Pennsylvania, with three counts of first and second-degree murder, aggravated assault, robbery and other charges, according to court documents.

In New Jersey, Gordon is charged with first-degree carjacking and weapons offences, New Jersey attorney general Matthew J Platkin said on Sunday.

“The string of violent acts … is the latest in a horrific litany of illustrations of how illegal guns and assault rifles can empower one aggrieved and disturbed actor,” Mr Platkin said. “We will pursue justice for the victims and hold the defendant accountable for his reprehensible actions.”

Gordon allegedly carjacked a vehicle in Trenton on Saturday morning before driving to Levittown in Falls Township, Pennsylvania, and killing his stepmother and sister, authorities said. He then drove to a second location in Levittown and allegedly killed the mother of his two children, authorities said.

The victims were identified by Bucks County district attorney Jennifer Schorn on Saturday as the suspect’s 52-year-old stepmother, Karen Gordon; and his 13-year-old sister, Kera Gordon; and 25-year-old Taylor Daniel, the mother of his two children, who were present at the time of the shooting in that home.

He is also charged with having beaten Ms Daniel’s mother with the assault weapon. She was taken to hospital for treatment.

He then carjacked a second vehicle in Morrisville and returned to Trenton, authorities said. Police surrounded a home for hours in the belief that he was there, but Gordon apparently slipped out before the police cordon went up. He was arrested at around 5pm, unarmed, when he was spotted walking down a nearby street, police said.

Officials in Pennsylvania said they could not yet reveal a motive for the attacks.

The mayhem forced the cancellation of a St Patrick’s Day parade and shut down a Sesame Street-themed amusement park, and a number of other businesses elected to close as well, authorities said. Authorities in Pennsylvania’s Bucks County issued a shelter-in-place order for some areas for several hours.

Mr Platkin said the crimes “alarmed and terrorised communities in Bucks and Mercer counties”.

Gordon is currently being held at the Mercer County Correction Centre. Trenton Police director Steve Wilson said Gordon would be extradited to Pennsylvania “at some point”.