NEW YORK (CBSNewYork) — A correction officer was slashed repeatedly by a group of inmates. The victim was nearly knocked unconscious during the attack.

Around 4:30 p.m., Officer Raymond Calderon was grabbed from behind, put into a choke hold and thrown on the floor. While on the ground, two other inmates approached Calderon and tried to slash him, sources said.

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Calderon could not call out for help because his oxygen was being cut off, sources told 1010 WINS.

The attackers slashed Calderon on the head, wrist and ears, and in multiple spots on his face, sources said.

As CBS2’s Valerie Castro reported, the attack was initiated after the inmate asked Calderon to open his cell — something the officer had to do manually, since the cell doors are not electronic, sources said.

According to Corrections Officers Union President Norman Seabrook, the attack was gang-related, and blames a system that doesn’t severely punish inmates who attack officers,  1010 WINS’ Al Jones reported.

“You can do whatever you want to do to a corrections officer and not worry about repercussion of any type,” Seabrook said.

The guard was initially taken to at Elmhurst Hospital Center, where he had been reported in serious condition, the department said. On Thursday night, he was at Queens Hospital in serious, but stable condition.

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According to Seabrook, the officer has received more than 20 stitches.

“Safety is (Correction) Commissioner (Joseph) Ponte’s top priority and he has zero tolerance for assaults on staff,” a department spokesman said in a statement. “The Department is seeking re-arrest of any inmate involved.”

Seabrook expressed concern about department policies in the wake of the slashing — that the department recently released new “use of force” guidelines that Seabrook said hte union was not consulted on.

“I’m thankful that the correction officer is alive,” Seabrook said. “It’s unfortunate that I do believe, as the president of this organization, that there will be a correction officer killed at the hands of an inmate – because there is no penalty to what they do.”

At least one of the attackers has been identified.

Calderon has been on the job as an officer for three years. He works in a division that handles young adults, 18 to 21-years-old.

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The Department of Corrections issued a statement saying there is zero tolerance for assaults on staff and is seeking the arrest of any inmate involved in the attack.