AMES - A report of a man with a gun on campus triggered an emergency alert and response at Iowa State University early Sunday morning.

It all started just before 1:00 A.M. at Willow Hall in Ames. That's a high rise ISU dorm located near Hilton Coliseum. Police questioned 20-year-old Jawon Jackson of Aurora, Illinois for hours. Authorities eventually charged him with going armed with intent, carrying a weapon on school grounds and first degree harassment.

The two gun charges are class "D" felonies that carry a possible term of up to five years in prison.

The call to campus police at ISU came in as a report of an armed man on the sixth floor of the dorm. Annette Hacker, an ISU spokesperson, said "apparently the person was not showing the gun in a threatening manner or brandishing it in any sort of way. He had it at his side."

Police went to the dorm and confirmed the witness' report. Minutes later, a campus-wide emergency alert was issued. Jackson was located about 20 minutes after the alert. He was unarmed when officers found him.

Police searched the dorm and grounds for hours but were unable to locate any weapon. Jackson was charged based on numerous eye witnesses accounts.

Several people staying on the 6th floor of the dorm told TV9 they heard a commotion at about one in the morning. Tayli Thompson, ISU freshman said "I went to the bathroom and there was like seven cops on our floor and they made us leave the room and they cleared our room and made sure it was OK."

The emergency alert via text messages, e-mails and phone calls went out to about 29,000 ISU recipients. Most were not on campus due to spring break. Only 30 of the estimated 500 dorm residents were home at the time of the incident.

University officials say Willow Hall has an electronic locking system so they presume someone let Jackson inside. It took about 40 minutes from the time of the initial campus-wide alert until the "all clear" was sounded.