No connection was immediately known between the victims and the shooter, she said. He had a bulletproof vest, an “AR-type rifle,” multiple magazines, a handgun and a police scanner.

Officers were flagged down at about 8:30 p.m., and multiple calls of shots fired came in from Kingsessing. Police found some gunshot victims, and as they were attending to them, they heard more gunfire, Outlaw said. Police later told Fox 29 that a fifth victim was found. He was chased into his home and shot to death. Bullet casings were found outside the home.

The suspected shooter was identified as a 40-year-old man. A second person was also taken into custody who may have returned fire at the suspect, but police did not know whether there was a connection between the two people, Outlaw said.

The chief said dozens of shell casings were found across an eight block area.

“You can see there are several scenes out here,” Outlaw said. “We’re canvassing the area to get as much as we can, to identify witnesses, to identify where cameras are located and to do everything to figure out the why,” Outlaw said.

Three of the dead were 20 to 59 years old, while the fourth, who had not yet been identified, was estimated to be between 16 and 21. The victim found in his home was 31 years old. All were male.

The two hospitalized victims are boys, ages 2 and 13. They were in stable condition, Outlaw said.

The shooting occurred a day after gunfire erupted at a holiday weekend block party in Baltimore, about 100 miles (160 kilometers) to the southwest, killing two people and wounding 28 others. The wounded in that shooting ranged in age from 13 to 32, with more than half minors, according to officials.

The Philadelphia violence is the country’s 29th mass killing in 2023, according to a database maintained by The Associated Press and USA Today in partnership with Northeastern University, the highest on record by this time in the year.

The number of people killed in such events is also the highest by this time in the year.

There have been more than 550 mass killings since 2006, according to the database, in which at least 2,900 people have died and at least 2,000 people have been injured.