With nerves frayed following the tragedy in Las Vegas Sunday night, social media lit up yesterday when students were told to shelter in place after someone reported there was a mass shooter on the campus of USC.

Police now say the incident was based on a bad report, apparently made by an adjunct professor who started yelling “active shooter” in class after telling students to lock the door and get down. “There was an 'episode' she had,” says Los Angeles Police Department Officer Mike Lopez.

The woman, described by police as a member of USC's faculty, was detained and remained in custody last night as officers questioned her and weighed whether she was eligible for a psychiatric hold, Lopez said.

“They are investigating whether that teacher should be placed on some type of hold,” he says. “They're investigating her to see why she did what she did.”

“It was reported a faculty member during class falsely told her students there was an active shooter in the building,” USC Department of Public Safety Assistant Chief David Carlisle said via email.

The LAPD received a 911 call about the situation at 12:17 p.m. yesterday, Lopez said. The USC Daily Trojan reported the incident took place at Fertitta Hall. The university immediately broadcast a “shelter in place” alert via its “TrojansAlert” system, Carlisle said.

There was a sizable response by the police and campus safety personnel. “In light of what happened in Las Vegas we had to treat it seriously,” Lopez says.

There was no shooting, and the faculty member was hauled away by LAPD, authorities said.

“LAPD and DPS continue to investigate what events led to the initial reports,” Carlisle said.

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