The suspect, whom a source told the St. Louis Post-Dispatch is 27-year-old Terry Joe Sedlacek, allegedly walked into the First Baptist Church, walked toward Rev. Fred Winters and killed him with a .45-caliber semiautomatic pistol, police said. Churchgoers then wrestled him to the ground as he brandished a knife, said Illinois State Police Director Larry Trent.
Sedlacek was the subject of a story in the Post-Dispatch about how Lyme disease had attacked his brain.
Stephanee Smith of the Madison County state's attorney's office said Sedlacek has been charged with first-degree murder and aggravated battery, but would not comment on a possible motive.
Winters later died of his injuries.
A tick bite dating back at least 10 years ago triggered a series of erratic behaviors and mental difficulties for Sedlacek, his mother, Ruth Abernathy, told the newspaper in August, adding that doctors struggled to pinpoint the cause.
"They didn't know, I didn't know," Abernathy said. "I just want my son back." She described her son in the article as an avid hunter and believed that's how he contracted the disease.
After spending time in a medically induced coma and receiving antibiotics, Sedlacek began to recover, the newspaper reported, however, his improved health did not last long.
Upon leaving the hospital, Sedlacek regressed and has spent the last several years having difficulty speaking. He takes several drugs, including an anti-seizure medicine, his mother told the newspaper.
"He takes enough medicine at night to knock a cow out, but he only sleeps two or three hours a night," Abernathy told the newspaper.
None of the about 150 worshippers attending the early morning service seemed to recognize the gunman, and investigators did not know details of Winters' conversation with him, police said, but they planned to review an audio recording of the service.
Police said investigators found no immediate evidence of a criminal background for the suspect. He said police were investigating whether a red Jeep parked outside the church belonged to the man.
The Jeep, which remained at the church Sunday night under State Police watch, was registered to the address of a 27-year-old man in an upscale neighborhood in Troy. No one answered the door at the residence Sunday.
Winters deflected the first of the gunman's four rounds with a Bible, sending a confetti-like spray of paper into the air in a horrifying scene worshippers, police said.
"We just sat there waiting for what comes next not realizing that he had wounded the pastor," said Linda Cunningham, whose husband is a minister of adult education at the 1,200-member church.
Winters had stood on an elevated platform to deliver his sermon about finding happiness in the workplace - titled "Come On, Get Happy" - and managed to run halfway down the sanctuary's side aisle before collapsing after the attack, Cunningham said.
Two worshippers tackled the gunman as he pulled the knife, and all three were stabbed - the gunman suffered "a pretty serious wound to the neck" while one worshipper had lower back wounds, Trent said.
Churchgoers knocked the gunman between sets of pews, then held him down until police arrived, said member Don Bohley, who was just outside the sanctuary when the shooting began.
"People came running out and told us to call 911," said Bohley, 72.
The gunman and 39-year-old worshipper Terry Bullard underwent surgery at St. Louis University Hospital and were in serious condition Sunday evening, according to hospital spokeswoman Laura Keller. The other victim, Keith Melton, was treated and released from Gateway Regional Medical Center.
"I would call it heroic," Trent said. "While many understandably were stuck to their seats, they took to action."