Four people were killed and two others, both minors, injured when a gunman opened fire in a Philadelphia neighborhood on Monday, police said.

The injured were described as 2-year-olds and 13-year-olds, both boys, who were in stable condition at a hospital, Philadelphia Police Commissioner Danielle M. Outlaw said at a news conference.

The gunman was described as a man with a semi-automatic rifle, a handgun, a body armor or ballistic clothing and a police scanner, police said. He also had several ammunition magazines, the commissioner said.

Responding officers heard gunshots and gave chase, and the suspect continued to fire, Outlaw said at an evening news conference.

He finally stopped when he was cornered in an alley and surrendered without incident, the commissioner said.

Police had initially said eight people were hit, but later revised the total to 6.

NBC Philadelphia reported that the attack took place in multiple locations.

Police investigate a shooting in Philadelphia on Monday.NBC10 Philadelphia

An additional suspect who may have picked up a firearm and returned fire was also in custody, police said at the news conference.

The deceased were described as being approximately 20 to 59 years old.

Police were investigating the violence and any possible motives.

This is a developing story. Please check back for updates.