The man remained silent as he stood before the judge Thursday. He will appear in court again Oct. 7, at which time his attorney will argue for his bail to be reduced.
"A million dollars is a high bail for a second-degree felony," said defense attorney Adam Elmore, who represented Stiles on Thursday.
Stiles was arrested more than a month after meeting with a crisis worker at Pioneer Valley Hospital in West Valley City on Aug. 12.
He told the crisis worker that he had plans to "kill as many people as possible" on Sept. 25 the anniversary of his mother's death according to court documents.
Stiles was arrested Monday. Two days before his alleged day of attack.
According to police, Stiles said he had "scoped and mapped out" sites at City Creek Center and at Cinemark Movies 10 in Sugar House. At City Creek, he planned to "just randomly shoot and kill people" at lunch time, police reported.
He then said he planned to go to the Sugar House movie theater at 1 p.m., when it is likely to be less crowded, allowing him to select his targets more carefully, according to police.
Stiles "expressed concern that if it is busy when the shooting begins, people will run everywhere making it difficult for him to select and shoot," police wrote.
Instead, he wanted to use handguns with silencers and start "shooting people's head's off" from the back of the theater.
He said he also planned to bomb a UTA bus or TRAX train as it passes the City Creek Center bridge in order to maximize deaths, police wrote.
Stiles said he would buy two automatic handguns with silencers and five extra magazines per gun, police wrote. He also has been researching bomb construction, police wrote.
He said he would not intentionally shoot children, but he said he will randomly kill people until he runs out of ammunition, police wrote.
But, he added, he would surrender to police because they are "faster shots."
When asked whether the man is likely suffering from a mental illness, Salt Lake County prosecutor Sim Gill said, "Hopefully as we go through the process, we'll get a little more clarity on that."
There was no discussion of the defendant's mental capacity or any potential illness in court Thursday. No family members looked on from the gallery.