A retired Yale employee carrying an unloaded gun and ammunition was arrested on the fringe of campus Thursday, and University officials believe he may have been targeting the nearby Human Resources office.

The gunman, John Petrini, 61, was spotted around 11 a.m. in a parking lot at 191 Whitney Ave., which is not Yale property but is on the same block as the HR office at 221 Whitney Ave. An unnamed individual called the Yale Police Department from a blue phone to report suspicious behavior, and officers responded within one minute.

“All of us have healthy imaginations, and if he was going to take the gun into a University building, that’s obviously a scary thing to contemplate,” University Vice President and Secretary Linda Lorimer said. “We presume that he was headed toward a University building because it’s all University buildings around there.”

Petrini, a physical plant employee who retired in 2002, was charged with breach of peace, threatening, carrying a dangerous weapon, carrying a weapon in a motor vehicle and driving with a suspended license. He is being held at the New Haven Police Department on Union Avenue and will be arraigned Friday in Superior Court.

No one answered the door at Petrini’s apartment in Westville on Thursday night. The New Haven Police Department denied access to him for an interview, and the YPD declined to release further details about the arrest.

The Yale community was notified of the incident in a 1:33 p.m. e-mail message from YPD Chief James Perrotti. University President Richard Levin said a text message alert was deemed unnecessary because the suspect was apprehended within a minute.

“I think this was a very serious situation, and we are deeply indebted to the good citizen who picked up the blue phone and reported suspicious behavior, and deeply indebted to the police department who were there within one minute of the call,” Levin said. “There were two squad cars very close by; really, this is a day of heroic deeds.”

Doris Rogan, the president of the Yale Unions Retirees Association, said she did not know Petrini or if he had a history of grievances with the University.