Yeah, it looks like you need to specifically blow up the vehicle first before you kill the player. I would suggest just using Nitramj's kill trigger and changing the kill messages to whatever you need, although you might want to ask him first.
Actually, it looks like you can just add custom damage types by adding this to the end of the file:
AddDamageType("sometypeofDamage", "%client has died for some other reason");
And then just specify which one you want. I don't know how to do that, I've never used his trigger before.