Phillies Fan Tasered

Did Philadelphia police use too much force on a Phillies fan?
As the Phillies were playing the St. Louis Cardinals at Citizens Bank Park a 17 year old boy ran onto the playing field waving a white towel. Security tried to track down the fan with no luck. In steps the police who subdued the 17 year old with a taser on the field.
The incident wasn't broadcast on TV, but has been uploaded on youtube by fans.
The Philadelphia police are investigating the incident to see if a taser was "proper use of equipment."
The teen has been charged with criminal trespassing and other charges.