BOSTON (CBS) — Boston University Police put all buildings “in and near the Kenmore Square area” in a “shelter in place” Tuesday afternoon as they search for a suspicious man who may have had a gun. The shelter in place has since been lifted.

Boston Police joined the university police officers in searching the Barnes and Noble in Kenmore Square.

Boston University tweeted that police were investigating “a report of a man who may have had a gun in the Kenmore Square area.”

Students in the area were alerted by automated text message to shelter in place.

“For people leaving class, it was a lot of panic and just running around and screaming,” sophomore Kyanna King said.

According to Boston Police, a 911 call from the area of 833 Beacon Street about a person with a gun prompted the search. An airsoft gun was recovered but nobody was arrested.

A BU alert said police were looking for a man last seen walking on the train tracks in the Kenmore Square area. The university’s police tweeted that the man was white with curly hair, had a beard, blue jeans, and a long sleeve shirt with black sleeves and some red and black.

The police activity near Kenmore was also caused MBTA delays in both directions on the Green Line. Service has since resumed but there are residual delays.

“I was just trying to get to class,” said Jacob Shaughnessy, a BU junior standing near the scene at Barnes and Noble. “They have the streets blocked off so we can’t walk.”