The Northwestern University issued an alert at 2.39pm local time (7.39pm GMT) warning anyone on campus to seek shelter and warning others to stay away from the campus.
The university tweeted: “NU EMERGENCY: Person with gun on Evanston campus. If on campus, seek shelter in safe place and stay until further notice. Others keep away.
“There is a report of a person with a gun in Engelhart Hall at the corner of Emerson Street and Maple Avenue.
“Evanston and Northwestern University police are on the scene. Seek shelter if in the area.
“Police continue to investigate a reported incident at Engelhart Hall. Remain sheltered or avoid the area.”
Colin Boyle, a student and photographer at the scene, said: “Northwestern University Police are investigating an emergency situation involving a person with a gun reported in Engelhart Hall on the Evanston campus.
“I was just told to clear the area a minute ago by an officer.”
Pictures taken by Mr Boyle show a large armed police presence descending on the campus.
The latest tweet from NU added: “Persons in Englehart Hall at the corner of Emerson Street and Maple Avenue should remain behind locked doors.
“Northwestern community members not in that area no longer need to stay behind locked doors. Anyone not in the area of Engelhart Hall should stay away.”
Chicago journalist Dawn Rhodes also tweeted: “Northwestern University says administration received a report of a shooting inside Engelhart Hall on campus, which is the graduate student residence hall.”
Northwestern students, faculty and staff received emergency alerts on their phones warning of someone with a gun on campus, Ms Rhodes added.
Northwestern University has around 21,000 student enrolled across its two campuses – Evanston is the main campus.
More to follow…
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