Suffolk County Executive Steve Bellone says the confrontation happened in Mount Sinai on February 24.
He says a 30-year-old driver, Christopher Cruz, had just been arrested for crashing a stolen Jeep into two police cars during a chase.
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Officials say the body camera footage shows two officers kicking the suspect several times while he was on the ground.
"I watched that video earlier today. What I saw was disturbing, unacceptable and something that cannot be condoned -- something I do not expect from our officers," Bellone said.
Other officers at the scene did not intervene.
As a result, two officers have been suspended without pay and four others, three officers and one supervisor, have been placed on modified duty.
There is an ongoing investigation into who else was involved.
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