Four people were shot and several more injured when a shopper opened fire by the checkout of a Walmart during an argument with another customer.
Police say the unnamed suspect fired at least 10 shots during the fracas in the Philadelphia suburbs.
Officials say the suspect and his female companion fled the shopping centre before crashing into a police car.
Both were arrested after the man fought with police, officers say.
Cheltenham Township Police Chief John Frye told a news conference on Tuesday night: "It seems there was some sort of altercation at the cash register.
"Words were exchanged."
He said the man "pulled the gun from the female's waistband and started shooting", just after 18:00 local time (22:00 GMT) as the Walmart was crowded with shoppers.
Two women and a man were all shot in the leg. Another person suffered a graze wound, and a pregnant woman was taken to hospital after falling.
The suspect and the woman who was with him - Montgomery County prosecutors say they are siblings - fled the scene in a Pontiac Grand Prix.
Witnesses saw them throwing the handgun out of the car's window.
Police say the pair then crashed into an empty Philadelphia police car, and fought with officers who eventually used a Taser to subdue the alleged gunman.
Two officers suffered minor injuries in the fight and were taken to hospital.
Philadelphia Police Chief Inspector Scott Small praised the officers.
He said: "They made this arrest initially thinking they were arresting somebody for trying to leave the scene of an auto accident and then realising it's a much more serious crime."
Chief Frye said that hospital reports suggest the shooter was "definitely on some type of drugs".
Police have not described the nature of the argument at the checkout and it is not clear if any party to the dispute was injured.
WPVI-TV captured footage of the suspect being brought to the police station in hand and leg cuffs.
"I'm sorry, man," he said to the camera. "I thought somebody was going to kill me."
More than 22 police departments responded to the crime scene, and Swat teams were called to clear the building and surrounding businesses in the plaza.
In a statement, Walmart confirmed that three of those injured were their employees.
"We are relieved that an arrest has been made and thankful that injuries sustained by three of our associates and a customer are non-life threatening," said Walmart representative Randy Hargrove.
https://www.google.com/amp/s/www.bbc.com/news/amp/world-us-canada-45199496
Police say the unnamed suspect fired at least 10 shots during the fracas in the Philadelphia suburbs.
Officials say the suspect and his female companion fled the shopping centre before crashing into a police car.
Both were arrested after the man fought with police, officers say.
Cheltenham Township Police Chief John Frye told a news conference on Tuesday night: "It seems there was some sort of altercation at the cash register.
"Words were exchanged."
He said the man "pulled the gun from the female's waistband and started shooting", just after 18:00 local time (22:00 GMT) as the Walmart was crowded with shoppers.
Two women and a man were all shot in the leg. Another person suffered a graze wound, and a pregnant woman was taken to hospital after falling.
The suspect and the woman who was with him - Montgomery County prosecutors say they are siblings - fled the scene in a Pontiac Grand Prix.
Witnesses saw them throwing the handgun out of the car's window.
Police say the pair then crashed into an empty Philadelphia police car, and fought with officers who eventually used a Taser to subdue the alleged gunman.
Two officers suffered minor injuries in the fight and were taken to hospital.
Philadelphia Police Chief Inspector Scott Small praised the officers.
He said: "They made this arrest initially thinking they were arresting somebody for trying to leave the scene of an auto accident and then realising it's a much more serious crime."
Chief Frye said that hospital reports suggest the shooter was "definitely on some type of drugs".
Police have not described the nature of the argument at the checkout and it is not clear if any party to the dispute was injured.
WPVI-TV captured footage of the suspect being brought to the police station in hand and leg cuffs.
"I'm sorry, man," he said to the camera. "I thought somebody was going to kill me."
More than 22 police departments responded to the crime scene, and Swat teams were called to clear the building and surrounding businesses in the plaza.
In a statement, Walmart confirmed that three of those injured were their employees.
"We are relieved that an arrest has been made and thankful that injuries sustained by three of our associates and a customer are non-life threatening," said Walmart representative Randy Hargrove.
https://www.google.com/amp/s/www.bbc.com/news/amp/world-us-canada-45199496
