Police surround a home in Trenton, N.J. on Saturday, March 16. A suspect has barricaded himself in the home and was holding hostages after shooting three people to death in suburban Philadelphia. Associated Press

Matt Rourke

TRENTON, N.J. — A gunman killed three people in their Philadelphia-area homes and then barricaded himself in a house in New Jersey's capital city Saturday, authorities said, in a string of violence that spread fear among the suburbs and prompted a major police response spanning two states.

The mayhem forced the cancellation of a St. Patrick’s Day parade and shut down a Sesame Street-themed amusement park. Authorities in Pennsylvania's Bucks County issued a shelter-in-place order for some areas for several hours.

The suspect, identified as 26-year-old Andre Gordon Jr., killed his stepmother, his teenage sister and the mother of his children in shootings that stretched into two homes in eastern Pennsylvania's Falls Township in the morning, Bucks County District Attorney Jennifer Schorn said.

Officials said they couldn't yet speak to a motive for the attacks. While Gordon had had some minor brushes with the law, they were “nothing that would indicate that anything like this would happen,” Falls Township Police Chief Nelson Whitney said at a news conference.

Police said Gordon was believed to be homeless. It was unclear whether he had an attorney or anyone else who could comment on his behalf.

After fleeing in a stolen car, then taking another in a carjacking in a store parking lot, Gordon holed up in a home in nearby Trenton, New Jersey, authorities said. By midafternoon, officers surrounded the house on a taped-off block, calling to Gordon through a loudspeaker and trying to persuade him to come out.

“Andre, get away from the windows. If you would like to surrender, dial 911 now,” one message went.

Neighbors gathered by the barricade to watch what was happening. The home's residents had been taken to safety with no injuries, the Trenton Police Department said.

Schorn said Gordon first broke into a home in the Falls Township community of Levittown and killed his 52-year-old stepmother, Karen Gordon, and his 13-year-old sister, Kera Gordon. Three other occupants, including a 14-year-old, hid as the suspect went through the house, searching for them, the district attorney said.

She said Gordon then drove to another home in Levittown and shot and killed 25-year-old Taylor Daniel, the mother of his two children, who were there. The victim's mother was bludgeoned with a rifle, Schorn said. Police said the injured woman is expected to recover.

Shaun Murphy, who lives in Levittown, said he was headed to the local St. Patrick's Day parade when he saw that the road had been blocked.

“All the neighbors were outside wondering what was going on, and then we got the notice about shelter in place,” Murphy said, recalling that he and his neighbors had just been talking the night before about “how great of a town and how great of a neighborhood it is.”

Schorn said that after the shootings, Gordon carjacked a vehicle in a parking lot in Morrisville, Pennsylvania, from a 44-year-old man who wasn't harmed. From there, officials said, Gordon drove to the home in Trenton.

Police in Middletown Township, Pa., said the suspect has ties to addresses in Bucks County and Trenton and “stays in Trenton primarily.”