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San Bernardino County Sheriff John McMahon ordered an immediate internal investigation Thursday into what he called "disturbing" video showing an arrest by deputies after a horse pursuit that was caught on camera by NewsChopper4.

Deputies appeared to use Tasers to stun a man and then beat him after the pursuit in San Bernardino County Thursday afternoon.

Aerial footage captured by NewsChopper4 showed the man falling off the horse, and then being stunned with a Taser by a sheriff's deputy.
The man then appeared to fall to the ground with his arms outstretched. Two deputies immediately descended on him and began punching him in the head and kneeing him in the groin.

The group surrounding the man grew to 13 sheriff's deputies as several appeared to kick, hit, and punch him dozens of times over a two-minute period.
In the two minutes after the man was stunned with a Taser, it appeared deputies kicked him 17 times and punched him 37 times and struck him with batons four times. Thirteen blows appeared to be to the head. The allegedly stolen horse stood idly nearby.

The man did not appear to move from his position lying on the ground for more than 45 minutes. He did not appear to receive medical attention while deputies stood around him during that time.
The man, identified as Francis Jared Pusok, 30, of Apple Valley, was hospitalized with unknown injuries, authorities said.

Three deputies were injured during the search. Two suffered dehydration and a third was injured when kicked by the horse. All three were taken to a hospital for treatment.
The series of events started when deputies from the Victor Valley station went to a home on Zuni Road to serve a search warrant in an identity theft investigation, authorities said in a news release.

The suspect took off in a vehicle and deputies initiated a pursuit through unincorporated Apple Valley, the town of Apple Valley and unincorporated Hesperia. The area is more than 80 miles northeast of downtown Los Angeles.
Pusok allegedly abandoned the vehicle 40 miles away from Hesperia in a place called Bowen Ranch where he took off running.

During a search on foot, with off-road vehicles and by helicopter, deputies learned the suspect had stolen a horse and rode it on dirt trails through rugged, steep terrain, causing numerous injuries to the horse.
A sheriff's helicopter inserted a team of deputies to take the suspect into custody. As deputies made contact with Pusok, the horse threw him off.

Deputies said the Taser was ineffective due to his loose clothing and a use of force occurred.
"I can certainly understand the concerns in the community based on what they saw on the video," McMahon told NBC4. "I'm disturbed by what I see in the video. But I don't need to jump to conclusions at this point, until we do a complete and thorough investigation. If our deputy sheriff's did something wrong, they'll be put off work and they'll be dealt with appropriately, all in accordance with the law as well as our department policy."

San Bernardino Superior Court records show Pusok has convictions for resisting arrest, animal cruelty, disturbing the peace, attempted robbery and failure to provide evidence of financial responsibility.