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.

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.

The suspect arrested after allegedly planning an elaborate mass shooting attack at Three Rivers Mall in Kelso, Wash., has been identified as a 14-year-old boy.