Infuriated students were forced to flee and cover as hundreds of officers in tactical gear invaded the school, a picture that is now commonplace in many US cities.
The gunman opened fire at two campus locations, turning the large university of about 50,000 students into a crime scene.
The victims' identities and ages have not been released by the police, nor have they indicated whether they were students.
Interim Deputy Chief Chris Rozman identified the shooter as a 43-year-old man who was not connected to the university.
We don't know why he came to school tonight to carry out this act, Rozman added.
According to data from the Gun Violence Archive, the attack, which occurred a few hours before the Marjory Stoneman Douglas High School shooting in Parkland,