A shooting scare shut down Northwestern University’s Evanston campus Wednesday afternoon when someone called police claiming he had opened fire inside a graduate residence hall, in a bogus report that authorities have deemed a “swatting” incident.

Evanston police received a call at 2:17 p.m. from a person who said he had shot his girlfriend inside an apartment at Englehart Hall, 1915 Maple Ave., about three blocks west of the main campus, according to Evanston Police Cmdr. Ryan Glew.

The call drew a massive police response, but officers found no one hurt or any evidence of a shooting. Officials soon determined that the unit where the shooting supposedly happened has been vacant since last November, and the call was traced to an area southeast of Rockford.

“It is a hoax,” Glew said.

The university first issued an alert at 2:39 p.m. warning anyone on campus to seek shelter, and urging others to stay away from the campus.

But Aiden Hartmann found out while working the front desk of the residence hall.

“I saw a cop car pull up and an officer got out with a gun. Then another pulled up with a bigger gun,” Hartmann said. “I was freaked out.”

Hartmann and another worker locked themselves in a bathroom for two hours, following updates on their phones.

Will Ewing, an Englehart resident, was walking toward the building’s back entrance when a handful of heavily armed officers told him to “Get back!” He waited out the investigation at a bakery in downtown Evanston.

“All my classmates were messaging each other to make sure we were OK,” Ewing said. “Teachers were pushing couches up against their doors.”

ALL CLEAR. Police have determined that the report of a man with a gun in Engelhart Hall was a hoax. It was made in a call to the Evanston Police Department. No danger to the community exists. Police are investigating the false report. — Northwestern (@NorthwesternU) March 14, 2018

Colin Boyle ran toward the scene with his camera to snap photos for NU’s student newspaper, The Daily Northwestern. Boyle said he texted his family members to let him know he was all right.

“My mother was hysterical,” he said.

Boyle and other students lauded the steady stream of updates from the school via text alerts, emails and automated phone calls. The lockdown was lifted by 4:15 p.m.

“This is the sort of thing that is a nightmare to a university,” NU spokesman Alan Cubbage said.

The caller claimed to have shot a woman who is a student, officials said. Authorities tracked her down and she was safe. It wasn’t clear if she had ever lived in the apartment or knew the caller.

Glew called it a “swatting” incident — a false report intended to provoke a SWAT team response, sometimes to divert police attention away from other crimes. No other incidents were reported on campus Wednesday afternoon, Cubbage said.

The caller is still at large.

Evanston Police press conference https://t.co/L2yEGnY6dL — Chicago Sun-Times (@Suntimes) March 14, 2018

It looks to be happening at the graduate building across the street from my apartment at Emerson & Maple pic.twitter.com/7mEpPZolyG — Kimberly Cotzias (@kimbrolyclaire) March 14, 2018

Area around Maple and Emerson are closed off with highly-armed officers on site #BreakingNews #Evanston pic.twitter.com/bnwtduwQXY — Colin B Photography (@colinbphoto) March 14, 2018

UPDATE: "Police continue to investigate a reported incident at Engelhart Hall. Remain sheltered or avoid the area." Per NUPD #BREAKING #evanston pic.twitter.com/k2UDMAvvVM — Colin B Photography (@colinbphoto) March 14, 2018

Police and Fire off in the area in the area of Emerson. Closures still in effect. Area is not secure and not safe. — Evanston, IL Police (@EvanstonPD) March 14, 2018

NU EMERGENCY: Person with gun on Evanston campus. If on campus, seek shelter in safe place and stay until further notice. Others keep away. — Northwestern (@NorthwesternU) March 14, 2018