A Del City girl, who said she witnessed her grandfather kill her brother, said the grandfather thought the boy was possessed by the devil.
The shooting happened in the 2700 block of Eagle Drive in Del City at the home where the grandfather was raising his grandchildren.
Police said Lochinvar Caldwell Junior was irrational, delusional and violent when they arrested him for attacking his neighbors on Friday night.
"Our neighbor showed up at our door, and he's completely naked, and he has a 10-year-old or so with him and he's kind of lost it," a neighbor said when she called 911.
The caller had no idea the horror police would later find inside Caldwell's home.
3/23/2014 Related Story: Del City Grandfather Accused Of Killing Grandson
"He was banging on the door, and I opened the door to see what was going on, and he kind of barged in," explained the 911 caller. "He's just going on and on about the church."
Once police arrested Caldwell, the granddaughter told police Caldwell had "gone crazy earlier in the day."
According to court documents, she said Caldwell forced her brother, Jaquelin Caldwell, into a bedroom where Caldwell told the 15-year-old boy that the boy was possessed by the devil.
The granddaughter said Caldwell pointed a pistol at Jaquelin's head, fired one shot and killed him.
"He was a happy-go-lucky kid to me every time he was around me," said the victim's cousin, Felicia Marzett. "He was always smiling."
Del City Police said the suspect was a preacher at one time.
"He was extremely religious before this occurred, at least by all appearances," said Major Jody Suit with Del City Police. "We don't know if that had something to do with the situation."
Caldwell also worked as a custodian for various schools in the area, including Oklahoma Christian School from 2003 to 2005.
One former student told News 9 Caldwell, or "LC" as he was known, always spoke about "God's glory" to the kids during lunch time in the cafeteria.
Del City police said they are looking into whether drugs played a role. They said they found a small amount of marijuana at Caldwell's home, and they are waiting on his blood results.