The FBI derailed a plot by a teenager who had planned to detonate a bomb at a Washington state shopping mall and shoot people as they fled a movie theater in the building, law enforcement authorities announced Thursday.

A Columbia County teen planned to set off an explosive at the mall in Kelso off I-5 and then shoot people as they fled the movie theater there, the FBI 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.