A man has been accused of plotting a shooting inside a cinema during a screening of the new Twilight film after his mother contacted police.
Blaec Lammers, 23, has been charged with first-degree assault, making a terrorist threat and armed criminal action.
His mother alerted police after fearing her son had purchased weapons similar to those used in a cinema shooting earlier this year in Aurora, Colorado, during a midnight screening of The Dark Knight Rises.
Bolivar Police Chief Steve Hamilton said: "Thankfully we had a responsible family member or we might have had a different outcome."
He said Lammers had been under a doctor's care for mental illness, while court documents said the suspect was "off of his medication".
Lammers' mother contacted authorities on Thursday, saying she worried that with this weekend's opening of the final film in the vampire series, her son "may have intentions of shooting people at the movie," police said.
She said she thought the weapons - two assault rifles and hundreds of bullets - resembled those used by the gunman who opened fire inside the Aurora cinema in July.
James Holmes, 24, is accused of killing 12 people in that attack.
Lammers told authorities he bought tickets for a screening of The Twilight Saga: Breaking Dawn - Part 2 in Bolivar on Sunday and planned to shoot people inside the cinema.
He also planned to "just start shooting people at random" at a Walmart store less than a mile away, police said.
Lammers also stated he wanted to stab a Walmart employee to death and followed an employee around in a store before officers intervened in 2009, according to police.
He said he had purchased weapons and if he ran out of bullets, he would "just break the glass where the ammunition is being stored and get some more and keep shooting until police arrived".
Police said Lammers bought one firearm on Monday and another on Tuesday. He then went to the town of Aldrich to practise shooting because he "had never shot a gun before and wanted to make sure he knew how they shot and how they functioned".
Mr Hamilton said it appeared the suspect obtained the firearms legally but that police were continuing to investigate "to determine how in fact he was able to obtain a permit".
Ashley Miller, who lives in a nearby town, said she has known Lammers for about a year and described him as "one of the sweetest guys I had ever met" but "very emotional," noting he would periodically stop talking to her.
Lammers is expected to appear in court on Wednesday.