18-year-old Joshua O'Connor was planning a similar attack at his high school in Everett, Washington. (About 30 miles north of Seattle.)
He already had two guns. He'd been researching improvised explosive devices. And he'd been filling his journal with detailed plans about what he wanted to do.
His journal entries included stuff about how he wanted to, quote, "make [it] count" and kill as many people as possible. And he'd been reading about other mass shootings to make sure he didn't make any mistakes.
But luckily, his GRANDMOTHER found one of the guns and the journal. And she's the one who called the cops and turned him in.
They arrested him on Tuesday, one day before the Parkland shooting. They think he also robbed a convenience store this week to help fund the mass shooting. So he's facing charges for first-degree robbery AND attempted first-degree murder.
A spokesperson for the school district issued a public statement thanking the grandmother for what she did. He said he knows how hard it must have been to turn her own grandson in, but it might have saved a lot of lives.