FORT WORTH, Texas >> Worried after a week of increasingly bizarre conversations with his younger brother, Glen Birdow drove to Fort Worth last weekend, hoping to understand why his brother was saying people were trying to kill him and that someone had stuck a needle in his arm.

Derrick Anthony Birdow was fidgeting and acting paranoid, but refused to check himself into a hospital. The 33-year-old married father of four insisted he was fine, his brother said.

But Derrick Birdow left his Fort Worth home Monday, passed by numerous churches and rammed his car into the side of Greater Sweethome Missionary Baptist Church in nearby Forest Hill. There, he got out of his car and beat the Rev. Danny Kirk Sr. to death with an electric guitar.

“The person that I knew was loving and caring, and he was not a killer,” Glen Birdow, 39, of San Antonio, told The Associated Press on Tuesday. “I just don’t know what happened. I’m so sorry for the pastor’s family.”

Derrick Birdow did not know the pastor or attend that church, though his wife might have gone there a few times, his brother said. Derrick Birdow enjoyed his job as a truck driver and didn’t have a history of mental illness, his brother said, adding that he didn’t believe that his brother used drugs.

Birdow died Monday after being found unresponsive in the back of a patrol car, where he was taken after officers subdued him with a Taser and handcuffed him, Forest Hill Police Chief Dan Dennis said.

Kirk, 53, died at the scene. Forest Hill police said Tuesday the investigation was continuing.

The Tarrant County Medical Examiner’s Office has not yet released how Birdow died. The Texas Rangers are investigating Birdow’s death because he died in police custody, Dennis said.

Tarrant County court records show that in 2004, Derrick Birdow pleaded guilty to aggravated assault with a deadly weapon and was sentenced to five years in prison. Glen Birdow said his brother believed a man had stolen money from him and police refused to help, and then he shot the man.

Derrick Birdow also served 35 days in jail in 2004 for a misdemeanor drunken driving charge, court records show. In 2000, he received 45 days in jail for misdemeanor assault of a family member, and in 1999 he was sentenced to 120 days in jail for possessing a controlled substance, court records show.

On Monday, his cousin, Christopher Henderson, said that Derrick Birdow had been “out of his head” the past week, saying people were after him.

When asked if Birdow used drugs, Henderson said that his cousin believed that someone may have given him drugs.

“He’s just been acting off the wall,” Henderson told The Associated Press outside of the church.