An Oklahoma "religious zealot" and heavy drug user nearly decapitated an acquaintance before calling 911 and admitting to the grisly slaying, police said.

Isaiah Marin, 21, ran from the Stillwater apartment Wednesday afternoon before being caught by police, covered in blood and still armed with the large blade, according to an arrest affidavit.

Following a trail of blood, cops found 19-year-old Jacob Crockett dead inside a nearby apartment.

The teen was the son of an Oklahoma Highway Patrol trooper and his "head was mostly severed from his body," Police Capt. Randy Dickerson told reporters Thursday at a news conference.

Marin had "strong" religious beliefs and was watching videos on YouTube "related to his Christian beliefs and the Book of Matthew" before the murder, according to an affidavit obtained by the Daily News. The documents also alleged that the pair had previous arguments because Marin disagreed with Crockett practicing witchcraft.

Marin and his brother were playing cards when Isaiah Marin picked up the weapon and pulled it from its sheath, swinging it around, the affidavit says.

His brother warned Marin to be careful.

"I would never cut you bro," Marin said, according to the affidavit.

But later on, the witness heard a noise "described as the sounds of someone getting stabbed," and looked up to see blood pouring from Crockett's chest and Marin holding the blade, according to the court document.

Marin reportedly had feuded with Crockett in the past because the victim was practicing witchcraft, the document said.

The brother fled, but Marin follow and tried to calm him down, promising to explain why he killed Crockett in letters from jail, the affidavit said.

Marin later called 911 and said, "I murdered someone," before rambling about magic and sacrifice and telling another dispatcher, "I hacked them to death with a machete," the document says.

A passerby later reported seeing Marin covered with blood and armed with the blade running down a highway.

Cops later found Crockett dead in the apartment kitchen and "evidence at the scene indicating the suspect was involved in the use of illegal drugs," Dickerson said.

Dickerson said religion was "not pertinent" to the murder case, the Tulsa World reported.

Marin maintained at least two Facebook pages, and on one wrote of troubled thoughts.

"Tried to take on a demon and God had to help me through the tough parts," he wrote in August. "Got to be careful with my words and pay closer attention to my emotions. Need to figure out how to keep on speaking when I'm with the presence of the Lord God."

Marin maintained at least two Facebook pages and wrote bizarre postings about religion and other ramblings.
"Not proud of my mistakes," he wrote days earlier. "Correcting them sounds painful."

Marin was charged with first-degree murder and ordered held without bail during an arraignment Thursday. He's next due in court Dec. 1.