Three people were wounded by gunfire at a Macy's department store in a shopping center outside Pittsburgh on Saturday, an FBI official said.
Local media said police were searching the Monroeville Mall for the suspected shooter.
FBI supervisory special agent Greg Heeb said he did not know if a shooter had been apprehended yet.
The wounded were taken to Forbes Hospital in Monroeville, about 12 miles east of Pittsburgh, where two were in critical condition and one was in fair condition, according to Dan Laurent, a hospital spokesman.
Police from jurisdictions outside Monroeville and FBI agents were called in to help look for the shooting suspect, Heeb said.
Police ordered the emergency department of the hospital to be locked down until the shooter is apprehended, said Jesse Miller, another spokesman for the medical facility.
A person who answered the phone at the Monroeville Police Department and a county emergency dispatcher declined to comment.
Terrelle Pryor, a National Football League player, said in a message on Twitter that he was at the mall and he saw two people who were shot.