The FBI and local authorities arrested a teen who allegedly planned a mass shooting with improvised explosives at a Washington state shopping mall.

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.