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.

The plot, described by one official as being “as serious as it gets,” involved a plan to shoot moviegoers at a Washington State mall as they fled an explosion.

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.