Two of the three victims were critically wounded at Monroeville Mall in Pennsylvania, authorities said. The third was in stable condition with injuries that were not life-threatening, Monroeville police Chief Kenneth "Doug" Cole said.
A motive for the shooting has not been determined. But Cole said he thinks the gunman knew one of the victims.
"We believe that one of those three people that were shot was a targeted individual, so this was not a random," the police chief told reporters Saturday night.
Allegheny County Police Lt. Andy Schurman said the two other shooting victims were apparently bystanders.
"The two innocent victims, we don't believe were the intended targets," he said.
Schurman said the targeted victim was the most seriously wounded.
The shooting took place in a Macy's store on the lower level of the mall. Two men and a woman were shot.
Witnesses at the mall, about 10 miles east of downtown Pittsburgh, described a chaotic scene.
"We were in Dick's (Sporting Goods), and all of sudden a whole bunch of people started running," Madison Strohl told CNN. "There were five shots fired right outside of the Macy's inside the mall ... it was really scary."
Two officers were working at the mall when the shooting occurred, Cole said. The mall was locked down and evacuated, with 15 agencies helping secure stores while authorities looked for the gunman.
A series of fights at the mall forced it to close temporarily in December, CNN affiliate KDKA
"There is a pattern here as you are well aware," the police chief said. "We don't know why the mall is having the problem it's having."
"Back in the '90s, we had shootings down there ... associated with gangs and drug activities," Cole said. "Maybe that's coming back around."