Unless there is more information to come out (always a possibility). It seems like he was just a guy that liked to shoot guns at the range, but used a high capacity magazine at the range which was illegal for him on a student visa (not illegal for him to possess, but illegal for him to insert in his, otherwise legal, gun).

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The warrant, one of three filed to search Zhao’s dormitory room and two vehicles, explained that Zhao kept a Bushmaster XM-15 rifle in the student gun lockers at Tech’s Public Safety Building. On Jan. 22, police were informed that Zhao had bought a 30-round magazine.

“It is not illegal for Zhao to own the two separate items,” the search warrant said. “If Zhao inserts a 30 [round] magazine into the rifle (changing the status of the rifle to assault firearm) is when it becomes illegal for him to possess due to his Student Visa status.”