A failing student out for vengeance opened fire inside the University of Arizona's School of Nursing in an attack that killed three of his professors, Tucson police said.
Mr Robert Flores, described as a nursing student who was struggling badly at the highly rated school, died when he turned the gun on himself yesterday.
Tucson Police Chief Richard Miranda said the three teachers killed were apparently deliberately targeted by the Tucson man (41).
Authorities identified the slain nursing professors as Ms Barbara Monroe (45), Cheryl McGaffic (44), and Robin Rogers (50).
Mr Flores is alleged to have shot one professor in her second-floor office and then two others in a classroom two floors above as students were doing a mid-term exam, school and police officials told reporters late last night.
"He apparently was struggling academically and was unhappy and frustrated at the fact that he was not doing well in the program," Ms Elizabeth Ervin, the university's vice provost for academic affairs, told reporters.
A health care official said Mr Flores was a former Gulf War veteran who worked as a licensed practical nurse at their facilities.