The San Bernardino County Sheriff's office ordered an investigation into the beating yesterday.
"The video surrounding this arrest is disturbing," San Bernardino County Sheriff-Coroner John McMahon said.
A sheriff's statement said Francis Pusok, 30, fled from deputies early in the afternoon as they tried to serve a search warrant in an identity-theft investigation. He eventually abandoned a car and stole a horse, but was tracked down by deputies.
KNBC-TV helicopter footage shows the man dressed in bright red clothing falling from the horse as a deputy runs up and uses a stun gun on him. The sheriff's department statement said the stun gun was ineffective.
KNBC-TV said up to 13 deputies eventually surrounded the man, and some of them kicked, hit and punched him dozens of times over a two-minute period.
Pusok's attorney, Jim Terrell, told KCAL-TV the video showed "thugs beating up my client."
The beating of Pusok, who is white, came as recent violent episodes by law officers dealing with suspects have provoked outrage after being captured on video, including the shooting death of an unarmed black man as he ran from a police officer last weekend in North Charleston, South Carolina.
Two deputies suffered dehydration, a third was kicked by the horse and all were taken to a hospital for treatment, the statement said.
