SALT LAKE CITY — A Utah man accused of plotting a mass shooting at an outdoor shopping center in Salt Lake City is set to make his first court appearance Thursday afternoon.

Jack Harry Stiles, 42, was booked into jail Monday on terrorism threat charges.

Tipped off by a hospital crisis worker, police learned in mid-August of Stiles plans to "randomly shoot and kill people" at the City Creek shopping center on Sept. 25, the anniversary of his mother's death. The upscale $1.7 million center is located in the heart of Salt Lake City — across the street from the Mormon temple.

Stiles also told investigators he planned to open fire at a movie theater across town, and then wire a bomb underneath a transit bus.

It's unknown if Stiles would have gone through with the plan. Court documents show Stiles didn't have any weapons, though he was planning to buy two guns with silencers and stock up on ammunition.

Motivated to take action by the Washington Navy Yard shooting last Monday, Salt Lake County District Attorney Sim Gill said he opted to take the threat seriously rather than regret not taking action.

After hearing about Stiles plan on Aug. 12, Gill said they began looking into his background and discovered that he had a history of mental illness and making threats.

Gill said he become fixated on the locations in his plan, mapping them out and visiting them over and over again. Charging document show Stiles had "scoped and mapped out the best spots" for hiding to "kill the most amount of people."

Stiles is in jail on $1 million bail.