An art teacher from Colorado is accused of embarking on a lethal stabbing spree with a “buck knife” crafted from an animal antler, allegedly targeting a man who later succumbed to his injuries and two women during Halloween night, according to police reports.

Authorities discovered 33-year-old Matthew Regnier from Colorado Springs “completely naked and covered in blood,” clutching a 2-year-old child, when officers arrived at the scene on the 1400 block of El Paso Street shortly before midnight on Friday. This information was detailed in an arrest affidavit accessed by Law&Crime.

The Colorado Springs Police were alerted by multiple calls regarding a domestic disturbance that evening. Upon their arrival, Regnier reportedly informed the officers that he had recorded the events leading up to and during the stabbing on his cellphone using “selfie mode.” He later asserted in police interviews that the incident was an act of self-defense, the affidavit states.

In the affidavit, Regnier consistently described an attack involving three individuals, alleging that one person attempted to bite his finger, another tried to strangle him, and a third made efforts to mutilate him, the document reveals.

Regnier recounted to the police that, during the alleged attack, he retrieved a “buck knife” from a closet and “defended himself,” as noted in the affidavit.

The male victim, identified as the child’s uncle, died early Saturday morning after being transported to a nearby hospital. Meanwhile, the two women survived the purported assault. The affidavit does not disclose the victims’ names, and their relationship to Regnier remains unclear.

One of the women allegedly told police that Regnier was keeping her and the other woman away from the child after changing their diaper. Regnier admitted to cops that he didn’t have a good reason for why the trio would attack him, according to the affidavit.

In the cellphone video that Regnier captured, he can be seen repeatedly holding the camera in “selfie mode” while one of the female victims was behind him on a bed, her arm seemingly around his neck, according to the affidavit. “Matthew was observed screaming about being choked and not being able to breathe, but repeatedly escaped from the supposed strangulation,” the document alleges.

Regnier can be heard screaming “something about his testicles” before he begins to repeatedly stab the woman, according to police. Regnier was “completely naked and … covered in blood” during the assault, the affidavit says, noting how he allegedly began stabbing the other female victim as well.

The male victim entered the bedroom after hearing the women screaming and was immediately attacked by Regnier, according to cops. Regnier’s cellphone video captures audio and video of the attack.

“Women are heard screaming as Matthew is observed repeatedly raising the large fixed blade knife and plunging it in the directions of [the man’s] head and body,” the affidavit says.

Police say they found the knife that Regnier used inside of the residence.

“The handle of the blade appears to be made from the antler of a deer or other game animal,” the affidavit alleges. “The knife [appeared] to be consistent with the décor of the residence, which included several animal skins and mounted skulls.”

Neighbors told local ABC affiliate KRDO that they saw Regnier outside the home handing out candy earlier in the night. Local officials confirmed to Law&Crime that Regnier is a former art teacher at the charter school Monument Academy who had his employment terminated over the weekend following his arrest.

The school district says he served as both an educator and a coach with the junior varsity soccer team at Palmer Ridge High School.

Regnier was taken into custody and charged with murder, attempted murder and assault. He was being held without bail at the El Paso County Jail with his first court appearance scheduled for Nov. 10.