In the hours since the University lifted the campus-wide lockdown, investigators from the New Haven and Yale Police Departments and other state and federal agencies have developed some leads as they turned their attention towards the 9:48 a.m. phone call that sparked the Monday’s events.

A press release issued by NHPD spokesman David Hartman on Tuesday morning indicated that “several people of interest” had been identified. Hartman also said that investigators are now analyzing surveillance footage of the area around 307 Columbus Avenue — the address closest to the phone booth from which the initial phone call stating knowledge of plans for a shooting at Yale was made. The footage does include images of the individual, a to-be-identified male, suspected of placing the call.

Additionally, Hartman confirmed that the NHPD is starting to believe the growing perception that a witness account of a man with a rifle walking near Lindsy-Chittenden Hall during the lockdown mistakenly reported an armed law enforcement officer as a potential gunman.

“Interviews are being conducted as the case progresses,” Hartman said in the release, which was issued at 1:21 p.m. “Detectives and Investigators from the NHPD, YPD and Special Agents from the FBI have been working around the clock on this case.”

Four SWAT teams assisted in an hours-long search of every room on Old Campus on Monday night.