BERKELEY, Calif. (KGO) -- The attack happened in Wheeler Hall, a classroom building that also houses offices for professors. Police say a female employee encountered the man in the restroom at 1:35 a.m. and told him the building was closed. He then followed her as she left.Sgt. Nicolas Hernandez with U.C. police said, "She had entered a restroom and asked the individual to leave and he didn't, so he assaulted her with the caustic chemical."The Berkeley fire department says the chemical was ammonia. The employee suffered from chemical burns. Paramedics worked on her at Wheeler Hall and then she was taken to a nearby hospital. Students and staff learned about the attack Wednesday afternoon after Cal police sent out a campuswide alert.Police aren't saying how the man got into the building or why he attacked as they continue their investigation.