(Reuters) - U.S. federal authorities said they have arrested a Florida truck driver who “was thinking about shooting up a church” in Memphis this week, making him at least the fourth person this month charged with plotting a mass shooting.

The Federal Bureau of Investigation arrested Thomas McVicker, 38, in Indianapolis on Monday after a friend in Alabama alerted agents to text messages he sent in which he described his plans for a mass shooting and suicide, according to court papers.

McVicker, who is from Punta Gorda but lives in his truck, is under treatment and according to his mother is on medication for schizophrenia, FBI Special Agent Ketrick Kelley said in an affidavit filed in U.S. District Court in Alabama.

It was not immediately clear if McVicker had an attorney. He appeared at a hearing at U.S. District Court in Indianapolis on Monday, the contents of which are under seal, a spokeswoman for federal prosecutors said.

Kelley said McVicker appeared to be planning to carry out a mass shooting at a church in Memphis, Tennessee, on Thursday. In recent days, law enforcement authorities in Ohio, Florida and Connecticut have said they arrested three men who planned unconnected mass shootings.

Since July 28, shooting sprees in Gilroy, California, El Paso, Texas, and Dayton, Ohio, killed 34 people.

McVicker’s messages violated a federal law against making interstate threats to commit violence, Kelley’s affidavit said.

The interstate tractor-trailer driver has a .45 caliber Ruger P90 handgun and sometimes uses cocaine and methamphetamine, the affidavit quoted his unidentified Alabama friend as saying.

Representatives of prosecutors and the FBI did not immediately reply to messages asking if McVicker acquired the gun legally.

McVicker, who complained of seeing “spiritual snakes and spiders in my bed at night,” first raised the prospect of a mass shooting in an Aug. 9 text, the affidavit said.

“I was thinking about shooting a church up but I’m afraid how it will affect my family in the flesh after I’m gone,” he wrote to his friend. “So I think I’m just gonna kill some people on the street and get away with it then kill myself.”

He raised the prospect of a church shooting again during an Aug. 14 phone call with his friend and had asked his employer for time off on Thursday, when he was to be in Memphis, the affidavit said.