By Kevin Murphy

KANSAS CITY, Missouri (Reuters) - A 20-year-old man is in jail in southwest Missouri on Friday on charges he planned a mass shooting at a theater during the showing Sunday of the new movie "Twilight."

Blaec Lammers told police in Bolivar, Missouri, that he bought two assault rifles and 400 rounds of ammunition with the intent of carrying out a shooting that would be similar to one that killed 12 people and wounded 58 during a Batman movie premier in Aurora, Colorado, last July.

Police announced Lammers' arrest on Friday. He was arrested Thursday and charged in state court with making a terrorist threat, armed criminal action and first degree assault, records show. He is being held on $500,000 bond.

Lammers' mother alerted police on Thursday that her son and bought weapons similar to those suspect James Holmes allegedly used in the Aurora shooting, Bolivar police detective Dustin Ross said in a sworn statement to the court.

On Thursday, Lammers, who is from Bolivar, told Ross that he bought the guns early this week for hunting, but then he began talking about recent shootings in the news, Ross said.

"Blaec Lammers stated that he had a lot in common with the people that have been involved in those shootings," Ross said. "Blaec Lammers stated that he was quiet, kind of a loner, had recently purchased firearms and didn't tell anybody about it and had homicidal thoughts."

Lammers said "he was going to shoot people at the movie theater" on Sunday and had bought a ticket for Twilight, according to Ross. Lammers said he was concerned he would run out of ammunition so he also planned to go to a Wal-Mart in Bolivar, shoot people at random and steal ammunition.

Lammers told police he went practice shooting with the guns on Tuesday because he had never shot a gun before and wanted to make sure he knew how they functioned.

The theater in Bolivar is a fourplex on the edge of downtown in the community of about 10,300 people, said Bolivar police Sergeant Shawn Curtis. Lammers did not resist arrest, Curtis said.

"We were happy with the outcome and with the work of our officers," Curtis said.

(Reporting by Kevin Murphy; Editing by Mary Wisniewski and Jackie Frank)