His name and image quickly spread worldwide as the perpetrator of the nation's second-deadliest school shooting. Facebook and Twitter lit up as people vented their fury at the man they believed was responsible.
In reality, Ryan Lanza was at work in New York City when the gunman opened fire at Sandy Hook Elementary School in Newtown, Conn., some 60 miles away, and a law enforcement official later identified his 20-year-old brother, Adam Lanza, as the culprit.
Ryan Lanza was interviewed by investigators but is not believed to have any connection to the killings. He told officials he'd had no contact with his brother since 2010.
The Associated Press, relying on a law enforcement official who turned out to be mistaken, initially reported Ryan Lanza was the shooter. Many other media outlets also reported as such, citing law enforcement officials.
Once he realized he'd been identified as the perpetrator, Lanza evidently whipped out his mobile device and began posting a quick succession of denials on Facebook, according to screen grabs purportedly taken from his Facebook page and posted online.
"IT WASN'T ME I WAS AT WORK IT WASN'T ME," said one message. Then, two minutes later: "I'm on the bus home now it wasn't me." Finally, three minutes after that, he posted an obscenity and repeated, "it wasn't me," the screen grabs showed.
A friend of Lanza's, former Jersey Journal newspaper staff writer Brett Wilshe, told the AP he "got really scared" when he began hearing the media reports about Ryan Lanza, and sent him a message on Facebook asking what was going on and if he was OK.
Lanza's reply, according to Wilshe, was something like: "It was my brother. I think my mother is dead. Oh my God."
Wilshe said he met Ryan Lanza through mutual friends and hung out with him about once a month.
"I really enjoy his company because he's a great guy," Wilshe said. He said Lanza never mentioned his brother, though "I didn't know him well enough to have gotten to know his family."
Katie Colaneri, 24, a radio reporter from Hoboken, said she met Ryan Lanza about a year and a half ago through mutual friends, and described him as "the nicest guy." She last saw him at a community meeting after Superstorm Sandy, and they spoke of how he had been without power for several days.
When she heard his name, she said, it left her in "absolute shock, and I could not fathom what I was hearing."