An investigation is underway after a young baseball fan who invaded the pitch was shot by a police officer with a Taser gun.
The Philadelphia Phillies supporter's invasion was brought to an abrupt end when he was hit by a bolt from the electroshock weapon during a Major League Baseball game against the St Louis Cardinals.
The 17-year-old, who has not been named because of his age, hurdled a fence before running rings around security guards who tried to catch him in vain.
But the police officer eventually caught up with him and felled him with a shot that brought him immediately to his knees.
The scene was witnessed by more than 44,000 fans, some of whom can be heard booing in video footage taken at the time.
Police spokesman Lt Frank Vanore told The Philadelphia Inquirer that an internal investigation would be held to determine whether the firing of the gun constituted "proper use of the equipment".
Phillies spokeswoman Bonnie Clark said: "The Police Department is investigating this matter and the Phillies are discussing with them whether in future situations this is an appropriate use of force under these circumstances."
The fan will be charged with criminal trespass and related offences, Clark said.