BOSTON (CBS) – An 18-year-old Melrose teen is being held without bail after being arraigned from his Boston hospital bed for the alleged stabbing of a Massachusetts state trooper on Route 495 in Amesbury on Thursday.

Nathan Aguilar has been charged with aggravated assault and battery and aggravated assault for the altercation in which he suffered a gunshot wound. The trooper, now identified in court paperwork as Stephen Torosian made an anguished radio call at noontime Thursday that he had been stabbed.

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Police say he was working a construction detail on the highway when he was suddenly ambushed by Aguilar, who had parked his gold minivan in the breakdown lane and walked toward the cruiser wearing a black ski mask.

According to police, a construction worker saw Aguilar make several stabbing motions toward the trooper. “He did so intending to cause serious bodily harm, if not death, to that trooper,” according to the Essex county prosecutor during the hospital arraignment.

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Nathan Aguilar in his hospital bed Friday during his arraignment. (WBZ-TV)

That’s when the worker heard the gunshot as police say trooper Torosian fired at Aguilar in self defense and was seen kicking a box cutter knife out of Aguilar’s hand as he lay on the ground.

Police say the knife was recovered at the scene. An investigation is underway to determine what provoked the attack.

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Aguilar is due in court December 20 for a dangerousness hearing.

Beth Germano