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.

Authorities thwarted a planned mass shooting and bombing at a mall in Kelso, Washington, with the arrest of an Oregon juvenile who had detailed intentions to carry out the attack.