The suspect involved in the fatal shootings of three people outside a Philadelphia-area suburb on Saturday morning has been arrested and will face charges in Pennsylvania and New Jersey, authorities said on Sunday.

According to authorities, 26-year-old Andre Gordon was found near a house in Trenton, New Jersey, after carrying out two separate shootings. Police had surrounded the 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 about 5 pm, unarmed, when he was spotted walking down a street a few blocks away, police said.

Gordon is suspected of killing his 52-year-old stepmother, Karen Gordon, his 13-year-old sister Kera Gordon and the mother of his two children, 25-year-old Taylor Daniel, the Bucks county district attorney, Jennifer Schorn, said.

He 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 offenses, New Jersey’s attorney general, Matthew J Platkin, said in a statement 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,” Platkin said. “We will pursue justice for the victims and hold the defendant accountable for his reprehensible actions.”

Schorn added that three other people, including a 14-year-old, hid in his stepmother and sister’s house as Gordon searched the property. Gordon is also believed to have used a rifle to bludgeon Daniel’s mother, who is expected to survive her injuries, said Schorn.

Authorities say they do not believe Gordon was armed at the time of his arrest.

Speaking at a news conference, the Falls township police chief, Nelson Whitney, said that there was “nothing that would indicate that anything like this would happen”, the Associated Press reported.

Gordon carjacked a vehicle in Trenton, New Jersey, about 8.40am on Saturday 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 killed Daniel, authorities said.

On Saturday morning, residents of Falls Township, where some of Pennsylvania’s wealthiest towns are located, were ordered to shelter in their homes temporarily as a manhunt for Gordon was under way.

The order was lifted shortly before 1pm, when police had cornered Gordon in Trenton.

Police said he carjacked a second vehicle in Morrisville, Pennsylvania, as he attempted to escape authorities.

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

Speaking to reporters in an earlier afternoon press briefing, a Falls township police officer said that at that time they believed he had a rifle styled after an AR-15.

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Such rifles have routinely been used in mass shootings across the country, prompting calls in some quarters for the weapons to be banned.

Nonetheless, the violence in Pennsylvania fell just short of the colloquial definition of a mass shooting, which the Gun Violence Archive – a non-partisan resource – classifies as a case involving at least four victims who are slain or wounded.

From 2015 to 2022, mass shootings involving an assault-style rifle left six times as many people shot and twice as many people killed as shootings involving other guns, illustrating how devastatingly efficient the weapons are at killing or maiming victims, according to the research group Everytown for Gun Safety.

Since January, Pennsylvania’s state legislators have introduced multiple bills proposing restrictions on firearms. Those measures include a proposal to ban rifles such as the AR-15.

The case leading to Gordon’s arrest was only one of multiple instances of violence with multiple shooting victims across the US over the weekend.

One person was slain and five others were wounded during a shooting at about 1.30am Saturday at a bar in Indianapolis. Police there said they later booked Nicholas Fulk, 25, on a count of murder, linking him to the deadly shooting through security camera footage and automatic license plate readers.

Meanwhile, at about 3am on Sunday, a shooting in north-west Washington DC killed two people and injured five others. Later in the day, police there said they were searching for another gunman.