A man has killed at least three people at a gymnasium in the US state of Pennsylvania, before shooting himself.

宾夕法尼亚一人在体育馆射杀至少三人，随后自杀。

Another 10 people were injured by gunfire in the town of Bridgeville near Pittsburgh, after the incident at the LA Fitness¹ Center.

An eyewitness² told a local TV station that a man entered an all-female dance class, turned off the lights, took two guns out of a bag and began firing.

"People everywhere were screaming. It was horrible," said the witness.

It is not known whether the gunman had any specific reason for targeting anyone at the gym.

"He did not say anything," Allegheny County police Superintendent³ Charles Moffatt said. "He walked right into the room where the shootings occurred as if he knew exactly where he was going."

"Each of us in the LA Fitness family are shocked and saddened by the senseless acts of violence that took place," said the gym management.