Three people have been rushed to hospital suffering from “potentially serious injuries”, according to the Austin-Travis County EMS.
A sign had been draped across the building’s sky bridge with the words “Tuition Pays for Bombs” before it was taken down.
But university police said the building was not under lockdown and is open.
The horror comes after a paramedic on a 911 call and a civilian were gunned down in Dallas by a shooter still on the loose.
Commenting on both incidents, Texas governor Greg Abbott said: “Our prayers go out to all those affected by today’s tragic events.
“As the investigations into these heinous crimes continue, I have offered all available state resources to both Dallas and the University of Texas to assist in any effort.”