Northwestern University warned people on campus to seek shelter Wednesday because of reports of a person with a gun on the Evanston, Ill., campus.

But shortly after 4 p.m., the Evanston Police Department posted on social media there was no evidence of a gunman or victim.

On Wednesday evening, the university posted on social media that the scare was the result of a hoax.

But on a day when gun violence was on many people’s minds — students walked out of classes at schools across the country, marking the one-month anniversary of the school shooting in Parkland, Fla., that left 17 dead — the warnings quickly went viral.

A spokesman at the university just north of Chicago did not immediately respond to messages Wednesday, but the school alerted the campus community with text messages and warnings on social media. A tweet from the university said there was a report of a man with a gun in Engelhart Hall, a dormitory.

Evanston police had warned the public on social media to avoid the area because of a “shots fired” investigation, and said the area “is not secure and not safe.”