Three people were fatally shot on Saturday morning at two separate residences in Falls Township in Pennsylvania, according to the authorities, who said they tracked the gunman to a home in Trenton, N.J.
The gunman, identified by the authorities as Andre Gordon, 26, drove a stolen vehicle and killed two people at a residence in Levittown, Pa., said the Falls Township Police, who responded to reports of a shooting around 9 a.m.
Mr. Gordon then shot and killed another person in nearby Morrisville before fleeing to a Dollar General parking lot, the authorities said.
He then stole a car at gunpoint there, the police said. The carjacking victim was not injured, the police said.
He was at large for a few hours before the police tracked Mr. Gordon to a home in Trenton, the Langhorne Borough Police Department said on social media. The police said a SWAT team was on the scene in Trenton, which is about 20 minutes from where the shootings occurred.
It was not immediately clear whether Mr. Gordon was in custody. Mr. Gordon knew the victims in Falls Township, the police said. A motive for the shootings was not immediately clear.
The police warned that Mr. Gordon was armed with an assault rifle and was believed to be in possession of other weapons.
A spokeswoman for Trenton Police Department said that the police were working with the authorities from Falls Township, the F.B.I. and New Jersey State Police.
A shelter-in-place directive that had been in place in Falls Township has been lifted. The authorities in neighboring townships had directed Sesame Place, a theme park in Bucks County, Pa., to close as a precaution and other shops followed suit on Saturday.