Three people were fatally shot on Saturday morning at two separate residences in Falls Township in Pennsylvania, according to the authorities, who said they have confined 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 his 52-year-old stepmother, Karen Gordon, and 13-year-old sister, Kera Gordon, in Levittown, Pa., according to Jennifer Schorn, the Bucks County, Pa., district attorney.
There were three other people, including a 14-year-old, in the home who hid as Mr. Gordon searched for them, Ms. Schorn said.
Mr. Gordon then drove to a second nearby residence where he killed Taylor Daniel, a 25-year-old woman with whom he had two children, Ms. Schorn said.
Four other people were in that home. One of them was Ms. Daniel’s mother, whom Mr. Gordon bludgeoned with an assault rifle. She was taken to a hospital and is expected to recover, Ms. Schorn said.
Mr. Gordon then fled to a Dollar General parking lot where he stole a car from a 44-year-old man who was uninjured, the authorities said.
Mr. Gordon was at large for a few hours before the police tracked him 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.
Christopher Clark, operations lieutenant at the Falls Township Police Department, said law enforcement authorities have Mr. Gordon contained in the house and they’re negotiating with him.
The residents in the home have been successfully evacuated with no injuries, said a Trenton Police Department spokeswoman, Detective Lt. Lisette Rios. The Trenton police said they were working with the authorities from Falls Township, the F.B.I. and New Jersey State Police.
The police warned that Mr. Gordon was armed with an assault rifle and was believed to be in possession of other weapons.
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.
Rebecca Carballo contributed to this report.