The “Oklahoma City Fertilizer Bomb” style bomb is heavily watched. ANFO just isn’t a good vector for a lone wolf anymore. With that said, any GWOT veteran with explosives training could make enough HME to make a mass casualty event à la OKC all over again. Maybe not all at once, right this second, but it’s a real threat vector. Worse, these training manuals available open-source and easy to replicate.

My neighbor is retired EOD, he has all Federal licenses manufactures explosives for the purpose of stump removal, if you can believe it, I’ve seen the process. It’s so easy a caveman could do it. Thankfully, no one really seems to do so. Mostly because manufactured firearms are easier to get ahold of. Or in Europe, smuggled weapons.

We cannot forget what insurgents in Iraq and Afghanistan did. It’s hubris to say “can’t happen here.”