Psh, no EMP.

Shaped charge (anyone can copy the google-able designs) and basic explosive compound that anyone can make / terrorists make all the time overseas. Simple ingredients, super dangerous. Ignited with an Arduino / micro-controller. Dude was already dead before the bomb went off, likely pills (if they didn't find a molten gun).

Or (Puts on tinfoil hat)

1. He used agency provided explosive compounds
2. He used agency provided equipment, timing equipment, and pre-made shaped charge forms (thank you spooks)
3. And they bypassed all that by having a missile skim the building across the way and blow up right inside the RV.

Psh, no EMP.

Shaped charge, I'm betting he used fertilizer and modified it haji style - check out his contacts, relatives, friends, etc.

Super easy to ignite such a bomb (chance you blow yourself up) and it doesn't take any smarts to make a half-decent shaped charge....a cone.

Or (Puts on tinfoil hat)

1. He used agency provided explosive compounds
2. He used agency provided equipment, timing equipment, and pre-made shaped charge forms (thank you spooks)
3. And they bypassed all that by having a missile skim the building across the way and blow up right inside the RV.