Hamilton said Saturday he didn't have details about Lammers' mental condition, although he said Friday that Lammers was under a doctor's care.
Lammers was questioned Thursday afternoon and told authorities he bought tickets to a Sunday "Twilight" screening in Bolivar and planned to shoot people inside. The town of roughly 10,000 people is about 130 miles southeast of Kansas City.
According to the probable cause statement, Lammers also said he planned to "just start shooting people at random" at a Walmart store less than a mile away. He said he'd purchased two assault rifles and 400 rounds of ammunition, 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," investigators wrote.
Police said Lammers bought one firearm Monday and another Tuesday, then went to Aldrich to practice because he "had never shot a gun before and wanted to make sure he knew how they shot and how they functioned."
Hamilton said it appeared that Lammers obtained the firearms legally.
He said his office has no information to indicate anyone else was involved but was interviewing people just to be certain.
Hamilton said it's "very difficult to say what (Lammers) would have done."
"I think he would have been adaptive," Hamilton said. "If one target wasn't available, I think he would have changed to something else."