By doing so, he may have destroyed valuable evidence that would help investigators understand his motives for killing his mother, 20 first-graders and six school employees at a Sandy Hook Elementary School in Connecticut Friday.
But in the age of cloud computing and multiple Internet-connected devices, authorities have no shortage of ways to follow his online footprints for clues, from acquiring his emails and search history to obtaining his online correspondence while he reportedly played "Call of Duty" on Xbox, experts said.
"Your Internet history is very telling," said Monique Ferraro, an attorney and digital forensics expert. "Even without a hard drive, if he was on the Internet, and most people are, investigators will be able to tell quite a bit about what he was doing, where he was going and what he was thinking."
Lanza, 20, was reportedly adept at computers, belonging to a technology club at his high school, according to the Associated Press. Yet he also left investigators with a relatively light digital trail to follow. In addition to destroying his hard drive, he reportedly did not have a Facebook or Twitter account.
Lanza's hard drive would have been valuable because it likely stored documents and records of his Web browsing history, said Jeff Pederson, the company's manager of data recovery operations Kroll Ontrack.
Kroll Ontrack, which specializes in data recovery, has retrieved evidence from hard drives damaged by floods, fires, and even a melted disk drive from the space shuttle Columbia, which was destroyed in 2003. Whether or not a hard drive can be salvaged depends on the extent of damage to what are called "platters," the small discs where the data is stored, Pederson said.
If those discs are shredded or broken, "the chances are very slim that we're going to be able to do something with that," Pederson said.
By damaging his hard drive, Lanza made it "tremendously more difficult" for investigators to piece together his online activities, said David McGroty, director of forensic operations at Flashback Data.
But not impossible. If he owned a tablet or smartphone, investigators could use data extraction software to view his contacts, calendar information, text messages, pictures, location history, and browsing history.
And if, for example, Lanza used Google for email or Web search, law enforcement officials will likely subpoena the company to gain access to the content of his emails or what sites he visited after conducting a Google search, according to experts. As the recent email scandal involving retired Gen. David Petraeus highlighted, it's very difficult to hide the details of correspondence from law enforcement -- even for the director of the CIA.
What's more, Lanza's reported obsession with "Call of Duty," a first-person shooter video game, may also offer clues. Microsoft's Xbox allows players to collaborate with each other online while playing the game. Such conversations, if they exist, are likely stored in the game console and could provide investigators with information that he sent other players and topics they discussed, Ferraro said.
"They're going to be looking at all of his stuff, his thumb drives, any removal media where he may have stored anything," Ferraro said. "They'll look at his Internet activity and see a lot of circumstantial evidence about what he was doing in the last several months."