Trenton, New Jersey - Three people were killed by gunfire in two shootings in a Philadelphia suburb Saturday, and the suspect fled and remains barricaded in a house in Trenton, New Jersey, the police and local authorities reported.

They said the suspect – identified as 26-year-old Andre Gordon, who was believed to be homeless – had stolen a vehicle before killing two people in a home in the Falls Township city of Levittown.

The victims were his 52-year-old stepmother and his 13-year-old sister.

Three people in the house managed to hide "as he went through the house searching for them," Bucks County district attorney Jennifer Schorn told reporters.

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The suspect then drove to another nearby residence where he shot and killed a woman with whom he has two children before using his rifle butt to bludgeon the woman's mother.

He then went to the parking lot of a nearby discount store, where he carjacked a Honda utility vehicle from a 44-year-old man before fleeing.

The man was not injured, according to Falls Township Sheriff Nelson Whitney.

The suspect then drove across the state line to nearby Trenton, New Jersey, where he remains holed up in a house, now surrounded by police officers, who were attempting to make contact with him.

People who had been in the house at the time "have been successfully evacuated with no injuries," said Detective Lieutenant Lisette Rios with the Trenton police department.

Whitney said the suspect was believed to be armed with an AR-15-style assault rifle, and police described him as "extremely dangerous."

Because the suspect crossed state lines, federal authorities, including the FBI, are aiding in the matter, Whitney added.

Residents in the area of the first shootings were urged to shelter in place, an order lifted after three hours.