A student carrying a single shot .50 caliber rifle was arrested on the Queens campus of St. John's this afternoon. WNBC reports that the male student had the gun in a bag, as well as a President Bush mask. Also:

Police sources said the man is a student of Guyanese descent who lived in a campus dorm. Sources said the student takes medicines for psychiatric issues and that police were investigating whether he had gone off his meds.

The police are searching all of the buildings as well, but they believe the student was acting alone.

The St. John's website notes the incident. Students have received at least two emails/text alerts from Public Safety. First alert:

A male with a rifle in a bag was apprehended on St. John's campus today. Public Safety officers quickly disarmed the suspect and have turned him over to NYPD.

Additional information will be forthcoming as it becomes available.

The message didn't mention which campus the gunman was on, leading to some initial confusion because there are campuses in Manhattan and Staten Island as well, leading them to update the with the news that gunman was at the Queens campus. And here's the other alert:

In response to the apprehension of a male with a rifle on our Queens campus, St. John's University has cancelled classes for the remainder of today, Wednesday, September 26

The NYPD is in control of the situation and is continuing its investigation of this incident. As part of their investigation, a large number of uniformed NYPD officers will be conducting a building by building search.

For the safety of all our community, those on the Queens campus should remain in place; those off campus are requested to stay away.

After the Virginia Tech shooting, many schools have promised to improve how they alert students on emergency events. Many offer email and text alerts to students, and there are also public safety websites (examples: CUNY, NYU, Columbia) which also show the various alerts.

Update: Fox 5 is reporting there may have been a second gunman. WNBC identifies the student as Omesh Hiraman, 22, and CityRoom reports that it's unclear if the weapon was loaded (the bag did not contain ammunition).