But any potential threat had been "neutralized," Castor said, though Musetti has not been charged with any crime.
The 1,150 students at Upper Merion were evacuated and sent home before classes started yesterday after a teacher spotted Musetti in a hallway. Moments earlier, the staff had been alerted to keep an eye out for Musetti because of Internet instant messages he had written in recent days that officials said appeared to be threatening.
In a news conference at the Upper Merion Township building, Police Chief Ronald Fonock - who called Musetti "a troubled young man" - said the systems put in place to protect students in the event of an intrusion had worked flawlessly. The school had been locked down and police notified immediately after the threat was spotted.
But what authorities had on Musetti, a 2006 Upper Merion graduate, was vague.
Officials said that Musetti and another former student had carried no weapons into the school, and none was found in Musetti's car. At the home where Musetti lived with relatives, police found a .22-caliber rifle - and said they were not sure whether there was ammunition to go with it.
They said that Musetti, who did not go to college and who worked in the area, had never been in trouble with the law. When found in the school, he was talking to a teacher.
He was described as having voluntarily committed himself yesterday to Norristown State Hospital for psychiatric evaluation.
Officials said they knew of no specific threat that Musetti had made against anyone. All they had, they said, was a series of "troubling" Internet messages from Musetti to unidentified students that had been turned in by their parents.
Some of the instant messages, they said, made references to the 1999 shooting at Columbine, in which 12 students and a teacher were slain before the two gunmen killed themselves, and to the April 16 shooting at Virginia Tech, in which 32 people, plus the gunman, died. Castor said that Musetti saw the gunmen as "his heroes," and that he at least somewhat fit the profile of the killers at those schools.
Officials said that the man who entered the school with Musetti, whom they did not identify, had been released after initially being arrested. They said he had gone in to say hello to former teachers.
Castor said that Musetti wouldn't be released from the hospital without a court hearing, and that his office would oppose a quick release.
According to the school district, police will be available at the school today to answer questions from parents and students.
Contact staff writer Tom Infield at 610-313-8205 or firstname.lastname@example.org.