BOSTON (CBS) — The head of the Boston Police Patrolmen’s Union is defending the use of force to subdue a suspect last week.

“I realize it’s not pleasant to see,” says Tom Nee. “But the officers used the training that they’d been taught. When a suspect won’t cooperate blows to the soft part of the thigh is an accepted submission tactic.”

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It was last Friday when police spotted a 16-year-old with a warrant for his arrest.

They say he resisted, and struck one police officer. Then it took nearly seven others to get handcuffs on him.

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The whole incident was caught on video by a student at Roxbury Community College. It clearly shows one officer punching the suspect, then kneeing him, as several others struggle to keep him down.

Boston Police Commissioner Ed Davis talks with WBZ News Radio about the incident.

The Suffolk County District Attorney has now appointed a special prosecutor to investigate.

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Thursday, City Council President Michael Ross said, “I think the video is disturbing, but I’m confident the Police Commissioner will conduct a fair investigation.”