Palton said the man, an Australian citizen with Somalian parents, is a high-risk person of interest.
"We have been monitoring him for a very lengthy period of time…What we will be alleging is that he was intending to use a firearm to shoot and kill as many people as he could," Patton said.
The man, who would face court, is believed to be acting alone.
"We are alleging that...he is a sympathizer of ISIS," Patton added.
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