Some of the most important clues about what drove Adam Lanza to mass murder probably sit on the computer that the reclusive, technical-minded 20-year-old used as one of his main contacts with the world, law-enforcement authorities said Wednesday.

Lanza attempted to destroy his computer's hard drive, the device that stores and retrieves data, before setting out on his killing spree Friday in Newtown, Conn. Police have declined to provide information on the extent of the damage to the drive, but investigators remain hopeful that it can be repaired.

Specialists, however, said that any effort to recover data may be thwarted if the hard drive's magnetic platters are shattered. If the damage is less severe, or if there are multiple platters in the computer, investigators may be able to glean useful information. Such recovery efforts are slow and costly, specialists said.

The computer was seized at Lanza's home soon after he killed his mother and went on to slay 20 children and six adults at Sandy Hook Elementary School before committing suicide.

In other news ... * 

The reaction to the Sandy Hook shooting can be seen at gun stores and self-defense retailers across the nation, with anxious parents buying armored backpacks for children and firearms enthusiasts stocking up on assault weapons in anticipation of tighter gun-control measures.

A spike in gun sales is common after a mass shooting, but the latest rampage has generated record sales in some states, particularly of rifles similar to the AR-15 Lanza used.

There was also an unusual increase in sales for armored backpacks designed to shield children caught in shootings, according to three companies that make them.

The armor inserts fit into the back panel of a child's backpack, and sell for up to $400, depending on the retailer. The armor is designed to stop bullets from handguns, not assault weapons like the one used in the shooting at the Newtown school.

* The family of Noah Pozner was mourning the 6-year-old, killed in the Newtown school massacre, when outrage compounded their sorrow.

Someone they didn't know was soliciting donations in Noah's memory, claiming that they'd send any cards, packages and money collected to his parents and siblings. An official-looking website had been set up, with Noah's name as the address, even including petitions on gun control.

Noah's relatives found out about one bogus solicitation when a friend received an email asking for money for the family. Poorly punctuated, it gave details about Noah, his funeral and his family. It directed people to send donations to an address in the Bronx, one that the Pozners had never heard of.

* President Obama has placedgun control at the top of his second-term agenda, redoubling his intention to tackle the problem of gun violence despite daunting political obstacles that have frustrated similar efforts for years.

On Wednesday, Obama sought to erase any doubts that he is prepared to stake his prestige on combating what he called an "epidemic of gun violence."

As a first step, Obama gave Vice President Joe Biden the task of coming up with specific proposals before the end of next month. Working with Cabinet members and outside organizations, Biden is to come up with ideas that likely will include actions Obama can take administratively to bypass potential clashes with Congress.

* Meanwhile, in Pennsylvania, U.S. Sen. Bob Casey said that he has changed his mind on gun control and now supports a ban on assault weapons and high-capacity magazines, the Inquirer reported.