Classes at Bothell High School near Seattle were cancelled Friday after a 63-year-old shop instructor was found by another teacher with a zip tie around his neck after an assault.

The man, identified as Cal Pygott, was apparently assaulted during after-school activities Thursday. Police said he was attacked with a blunt object, and suffered serious injuries. He was apparently struck from behind. Officials didn't say if he got a look at his assailant.

He was found staggering around outside a classroom, where another teacher helped him, and removed the zip tie from his neck. It was not disclosed if it had blocked his airway. Pygott was released from the hospital Friday.

Officials didn't say if Pygott was the subject of any previous threats, and the school superintendent said in their eight years working in the Northshore district, this was by far the most shocking incident that has occurred.

Police are studying surveillance cameras to try to determine who the assailant was, or if there were more than one.