Investigators have not managed to retrieve any data from a computer they took from the house where the gunman in the Newtown, Conn., school shootings lived with his mother because he had all but destroyed the hard drive, a senior law enforcement official said Monday.

‘'It looked like he took steps to damage it — he smashed it,’’ said the official, adding that the FBI had joined the State Police in an unsuccessful effort to recover data that might lead to some understanding of what might have prompted the gunman, Adam Lanza, 20, to go on a rampage.

He began at his own house, shooting his mother, Nancy Lanza, with one of the five weapons that were registered to her there, and then moved to Sandy Hook Elementary School in Newtown, where he killed 20 first-graders and six school employees with a semiautomatic assault rifle. Some were hit 11 times.

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But the official said it did not appear that Lanza had left any letters or notes that would offer a motive for the killings, or explain why he had targeted the school.

As investigators continued to examine other evidence they had seized, the first funerals were held on a gloomy and chaotic day that brought word of a second survivor, a school employee who was wounded but had not been mentioned in earlier accounts of the carnage. Her name was not immediately released. The other survivor at Sandy Hook was identified as the school’s lead teacher, Natalie Hammond, 40.

The spokesman for the State Police, Lt. J. Paul Vance, said investigators would ‘‘examine everything and anything,’’ including cellphones, game consoles and ‘‘anything that can provide us with information’’ about Lanza and his motivations for the rampage.

But he provided no indication as to why Lanza had trained such firepower on the students in two classrooms at the school. Vance said Lanza had ‘‘no connection’’ to the school.

Lanza lived with his mother in a house about five miles away. She owned the guns he fired and the car he drove to the school.

Agents from the Bureau of Alcohol, Tobacco, Firearms and Explosives have determined that Lanza and his mother had visited firing ranges, sometimes together, sometimes separately, according to a federal law enforcement official. The agents have been interviewing firearm dealers in Connecticut to ‘‘get a clear picture of what activities took place’’ before the shooting, said the official, who would not identify the shooting ranges.

Monday brought a new and grim reality to schools across the country. In some places, armed officers greeted students amid tighter safety procedures, and education officials rethought their security policies. There was a large police presence outside a funeral home in Newtown after what Lt. James Perez of the Fairfield Police Department described as vague threats of protests and ‘‘stupid comments’’ on the Internet and on social media.

In Ridgefield, Conn., a half-hour’s drive from Newtown, the police received a call about a ‘‘suspicious’’ stranger dressed in black and carrying what appeared to be a rifle. He was said to be walking from a train station toward an elementary school before the school day had even begun.

Officials ordered a lockdown — effectively a lockout, since most of the students were on school buses that had not arrived yet. The buses were diverted to another school while the police searched the area. The students were let into the school about four hours later, and the police eventually arrested a suspect, Wilfredo M. Seda, 22, of Redding, Conn. He had an umbrella that ‘‘had the outward appearance of a Samurai sword,’’ the Ridgefield police said in a statement. He was charged with a breach of the peace.

In Newtown, classes were canceled Monday, and it was not clear whether students would ever attend classes in the Sandy Hook building again. Gov. Dannel P. Malloy approved an arrangement for the students to use a surplus school building a few miles away, in Monroe, and the children’s desks from Sandy Hook were moved there.

Lanza’s mother had divorced his father, Peter J. Lanza, in 2008, citing ‘‘irreconcilable differences’’ after 27 years of marriage. The couple had joint custody of Adam Lanza, but he was expected to ‘‘reside primarily with the mother,’’ according to divorce settlement papers filed in Stamford Superior Court.

The settlement was generous to Nancy Lanza and her sons — Adam had an older brother, Ryan. She got the family house, and Peter Lanza was to provide $240,000 a year in alimony starting in 2010. The amount was to increase annually through 2015, when it was to reach $298,800.

But while the settlement said Peter Lanza was responsible for paying the two sons’ college tuition and for providing ‘‘a car for their son Adam’’ — if Adam wanted one, and if Nancy Lanza paid for the insurance — Nancy Lanza was responsible for unreimbursed medical expenses. Those, the settlement said, included ‘‘hospital, optical, psychiatric, psychological and nursing expenses.’’

A mediator who worked with the couple told The Associated Press that they told her that Adam Lanza had received a diagnosis of Asperger syndrome.

Some details about Adam Lanza’s teenage years also emerged. Around the time the divorce was in the works, he attended Western Connecticut State University as a part-time student. He did not make much of an impression.

Prof. Renate Ludanyi, the director of the university’s German studies center, said that Lanza was a student in her class during spring 2009, according to her grade books. But she said her memories of him were faint.

‘'If at all I remember a quiet kid, a quiet young man sitting by the door,’’ she said.

Lanza dropped out of the class before the final grades were compiled. His grades until then had been ‘‘medium to not very good,’’ she said.