Updated

A Utah man accused of plotting a deadly attack on a luxe outdoor shopping center in the heart of Salt Lake City this week told investigators he planned to "just randomly shoot and kill people."

Jack Harry Stiles, 42, told a crisis counselor he was preparing to "kill as many people as possible" on Wednesday because it marked the anniversary of his mother's death, authorities said.

Jail records show Stiles was booked into the Salt Lake County jail Monday and remains there on $1 million bail. The Salt Lake Legal Defender's Office said he didn't have any attorney yet.

Court documents show he didn't have any weapons but was planning to buy two guns with silencers and stock up on ammunition.

His motive was unclear, but he may suffer from a mental disorder, prosecutor Sim Gill said.

"Hopefully as we go through the process, we'll get a little more clarity on that," Gill told The Salt Lake Tribune. "People who do need help fall through the cracks. Our mental health system is in absolute crisis.

Stiles planned to open fire at City Creek shopping center, the $1.7 billion centerpiece of Salt Lake City that spans two city blocks, charging documents say.

He also told investigators he planned to "shot people's heads off" at a movie theater across town, and then wire a bomb underneath a transit bus.

His plan was to carry five extra magazines, and he had "scoped and mapped out the best spots" for hiding to "kill the most amount of people," authorities said.

Charging documents don't say why Stiles wanted to do it, whether he offered a reason, or why the anniversary of his mother's death was a motivating factor.

Police first learned of the plan Aug. 12 when a West Valley police officer was dispatched to Pioneer Valley Hospital by a crisis worker. The charging documents do not say why Stiles was at the hospital.

Investigators couldn't say whether Stiles was capable of carrying out his plan, but took the threat seriously.

"The thing that gave us concern was the amount of planning and detail," Sim told KSL-TV.

Court records show Stiles had a run-in with Utah Transit Authority in October 2011 when he was charged with theft of services. Stiles failed to appear in court on the charge, was arrested on a warrant and booked in jail for a time. Most recently, he planned to fight the charge at a trial.