A 14-year-old Oregon boy now charged with attempted murder in an alleged bombing and mass shooting plot had become isolated by a recent move and then radicalized by an online extremist network, his lawyer said.

A teenager in Oregon planned to set off an explosive at a shopping mall in Washington state and shoot people as they fled the movie theater there, said law enforcement officials, one of whom said the plot "was as serious as it gets.

An Oregon teen has been arrested in connection with an alleged mass shooting plot targeting the Three Rivers Mall in Kelso, in southwestern Washington, officials said.