NEW HAVEN, CONN. (CBSNewYork) — Yale University was locked down and under a “shelter in place” order for almost six hours Monday, following the investigation into an anonymous caller’s claim that his roommate was on his way to the campus to shoot people.

Calhoun College and the Old Campus of Yale were also in lockdown but the order was eventually lifted.

University officials later said the warning about the person with the gun was likely a hoax.

As CBS 2’s Lou Young reported, the incident started around 10 a.m. Monday when New Haven police received a 911 call from a pay phone booth near the school reporting a person with a gun near the Old Campus.

The caller also told authorities “that his roommate was on his way to the university, to Yale University, to shoot people,” New Haven police officer David Hartman said.

Around 11 a.m., two witnesses reported seeing someone carrying a long gun in the area, but Hartman said it’s possible those people may have seen law enforcement officers responding to the scene, 1010 WINS’ Al Jones reported.