The man who fatally shot two people at a White Settlement Church on Sunday before being killed by church security has been identified as a 43-year-old Keith Thomas Kinnunen, a River Oaks man with a long criminal history and described by his ex-wife as "battling a demon" and "not nice to anyone."

Kinnunen was identified as the shooter Monday morning by two law enforcement sources familiar with the investigation. NBC 5 has learned his criminal past included charges of assault, theft, arson and possession of an illegal weapon in Texas, Oklahoma and New Jersey.

Kinnunen was believed to have been wearing a disguise, including a fake beard and wig, when he stood up from a pew during communion, pulled a shotgun from his clothing and opened fire inside a North Texas church, killing 64-year-old Anton Wallace, a church deacon from Fort Worth, and 67-year-old Richard White, of River Oaks.

Volunteer church security immediately approached Kinnunen and returned fire, killing him.

The man who fatally shot two people at a White Settlement Church on Sunday before being killed by church security has been identified as a 43-year-old Keith Thomas Kinnunen, a River Oaks man with a long criminal history and described by his ex-wife as “battling a demon” and “not nice to anyone.”

"I was so surprised because I did not know that so many in the church were armed," Isabel Arreola said, telling the Fort Worth Star-Telegram that she was sitting near the gunman, had never seen him before, looked like he was wearing a disguise and that he "made her uncomfortable."

The FBI is working to identify the shooter's motive. Matthew DeSarno, the Special Agent in Charge of the FBI's Dallas field office, said the gunman was "relatively transient," but had roots in the area.

Britt Farmer, senior minister at West Freeway Church of Christ, confirmed Monday that the church had provided Kinnunen with food on multiple occasions, but wasn't sure of the date of the most recent gift. The church also confirmed Kinnunen had asked for money, but was not given any.

Church leaders said they did not recognize Kinnunen on Sunday morning because he was in disguise, confirmed the son of the church's senior minister. In fact, many lifelong church members said they immediately noticed the strange man because it appeared he was wearing a large, fake beard.

Tarrant County Sheriff's Office

Kinnunen's ex-wife said he had a bad drug habit and lost touch with reality.

"We knew he was crazy but not like this," Angela Holloway said. "I don't wish this on anybody. I feel sorry for the victims. I really do."

The two divorced in 2010 after being married for eight years.

The West Freeway Church of Christ had previous contact with the shooter, identified Monday as Keith Kinnunen, church officials say.

"Mentally, I know he was mentally ill," she said in an interview Monday. "The last time he spoke to us he just wasn't in his right mind. I didn't know how to go about talking to him about it."

The two last talked about three years ago, she said. Holloway has since remarried and now lives in Fort Worth.

"He's gone," Holloway said. "There's nothing I can do about it, but I'm glad it got stopped."

Kinnunen then moved to Oklahoma and reconnected with his first wife, Cindy Glasgow-Voegel. She filed for a protective order in January 2012 in Grady County, Oklahoma.

In a statement, she wrote, "Keith is a violent, paranoid person with a long line of assault and batteries with and without firearms. He is a religious fanatic, says he's battling a demon ... He is not nice to anyone."

In that same 2012 document, Glasgow-Voegel said Kinnunen showed up at her home in October 2011 unannounced, with no money or vehicle, asking to see his son. She said she got him a trailer and a job and that he quit the job, assaulted a man in Tuttle, Oklahoma, and was in the county jail. She said their 15-year-old son was "terrified" of his father and that he threatened her should she try to keep them apart.

In the protective order, the woman said her son was visiting his father when he set several fires around Tuttle and that her son recorded the arson but didn't saying anything out of fear of retaliation. An arrest warrant affidavit filed in December 2011, that included a statement from his teenage son, said Kinnunen set a cotton field on fire using lamp oil, tampons and a lighter. His son also said his father liked to play "fire football," where he soaked a football in a flammable liquid, lit the ball on fire and then they'd toss it back and forth. The teen told police he thought it was unsafe but that he was "afraid he might get mad at me if I asked to stop."

Jack Wilson, West Freeway Church of Christ’s head of security, tells NBC’s Blayne Alexander he feels like he “killed an evil,” not a human, when he shot the gunman who killed two people during Sunday’s church service.

In November 2011, two months before his ex-wife filed the protective order, Kinnunen was charged with aggravated assault and battery in Grady County, Oklahoma, after he repeatedly hit a man in the face, breaking his nose.

Locally, Kinnunen had a criminal record in Tarrant County including charges of aggravated assault with a deadly weapon in 2009 and theft of property in 2013. River Oaks police arrested him in 2009 and 2015 on warrants for unpaid traffic tickets, River Oaks, Deputy Police Chief Charles Stewart said.

Court records show Kinnunen sued a Fort Worth nightclub, the OK Corral on the South Freeway, in 2007 alleging he was “relaxing” in the club when attacked by several of its employees, including the manager.

His complaint said he “suffered serious and disabling injuries” and would continue to “suffer severe mental and physical pain and distress in the future.” The operators of the club denied the allegations and the case was eventually settled out of court, according to the records.

Texas Attorney General Ken Paxton says he hopes more houses of worship learn from Sunday’s shooting at the West Freeway Church of Christ in White Settlement and take a similar approach to being prepared for an attack. The church has an armed security team that includs volunteer members of the congregation and stopped an active shooting on Sunday within six...

Kinnunen also was arrested in September 2016 for possession of an illegal weapon in Linden, New Jersey, after he was found taking pictures outside an oil refinery, WNBC in New York has confirmed. Kinnunen said he was traveling from Texas, was homeless and was taking photos of “interesting sites.”

At the time of his New Jersey arrest, Kinnunen also had a warrant for his arrest in Oklahoma for aggravated assault, mycentraljersey.com reported.

NBC 5 has learned Kinnunen was once licensed as a landscape irrigator and backflow prevention assembly tester.

Stewart said Texas Rangers and other law enforcement officers searched Kinnunen’s home on Sunday soon after the shooting at the church.

NBC 5's Jack Douglas Jr., Maria Guerrero and Frank Heinz contributed to this report.