September 25, 2012 -- Updated 0049 GMT (0849 HKT) University of Florida student Christian Aguilar, 18, disappeared last week after an altercation in Gainesville. NEW: A "person of interest" has been charged with depriving a victim of medical care Christian Aguilar disappeared Thursday after a fight with another man, police say (CNN) -- Nearly 100 people, including police, volunteers and family members, were searching Monday for a University of Florida student who went missing four days ago in Gainesville. Aguilar, 18, disappeared last week after an altercation over a girl, his father told CNN affiliate WCJB. According to police, Aguilar and another 18-year-old man had an altercation on Thursday. The second man told investigators he left Aguilar in the parking lot, but searchers using helicopters and scent dogs failed to turn up any trace of him, police said Sunday. Authorities have said the man is a "person of interest" in the case and charged the 18-year-old with depriving a victim of medical care, a third-degree felony. He underwent a psychiatric evaluation Monday after he told investigators that he wanted to kill himself and was subsequently booked in the Alachua County Jail, Officer Ben Tobias said. Family members, who have plastered the area with fliers and taken to Twitter to generate leads, have invited a nonprofit search group to help look for Aguilar alongside family members and police. American couple killed in St. Maarten Search for missing climbers suspended Body of missing Amtrak passenger found CNN's Joe Sutton contributed to this report.