TUCSON, Ariz. -- Robert Stewart Flores Jr. struggled as a nursing student at the University of Arizona. Classmates said he tangled with instructors and annoyed fellow students.

"He came across as very aggressive and mean and seemed to have a lot of issues with being angry," said Lori Schenkel, a fellow nursing student.

Authorities said Flores' anger boiled over Monday when he allegedly shot three of his professors to death during a rampage at the College of Nursing that sent dozens of terrified students diving for cover.

Officials said the 41-year-old Gulf War veteran had been carrying five handguns and at least 200 rounds of ammunition. After shooting the three staff members, Flores turned one of the guns on himself.

School closed

The nursing school remained closed Tuesday, with police tape blocking access. Many employees at the medical school complex embraced as they went into work. Some were dressed in black.

"I feel terrible this morning," said Melody Pelot, 55, who works at the college of medicine. "As I walked past the police tape I thought, 'This is just mind boggling. Someone lost their mother, their wives, in that building.'"

Killed were Robin Rogers, 50, Cheryl McGaffic, 44, and Barbara Monroe, 45.

Flores worked at the Veterans Affairs hospital in Tucson as a licensed practical nurse and was studying to become a registered nurse. He was employed by a nursing agency, said Spencer Ralston, associate director for the Southern Arizona VA Health Care System.

Flores failed a pediatric nursing class and was struggling in a critical care class this term, said university vice provost Elizabeth Irvin. An exam on critical care was being administered when the gunman burst into McGaffic and Monroe's classroom.

Concealed weapons permit

Schenkel said Flores bragged to pediatrics classmates last year that he had received a concealed weapons permit. She said he seemed to enjoy calling attention to himself by asking inappropriate questions and challenging instructors. He failed that class and had to take it again, Schenkel said.

"Most of the people in class didn't like him," Schenkel said. "He was very obnoxious and rude."

William Gordon, a registered nurse who said he worked with Flores at the veterans hospital and knew him for three years, said he saw nothing that would foreshadow violence by Flores.

"He was very nice, very intelligent, very well-spoken," Gordon said. "I never heard anything violent period."

A year and a half ago, instructor Melissa M. Goldsmith told police that Flores said he was having problems with a paper but also had a lot of problems other than school, according to the university police department report filed on April 24, 2001.

"He was depressed and thought about 'ending it all.' Flores then stated he 'might put something under the college,"' according to the report, which was provided to The Associated Press on Tuesday by university police.

University police chief Anthony Daykin said the department took no action after the report because an administrator and faculty member had talked with Flores and felt no other action was necessary.