Rattlesnake blood - not hazmat level material in my uneducated opinion, but I live in Arizona, where we have plenty of rattlesnakes and I've killed snakes myself before with a shovel. Once it's dead, toss in trash and if there's 'stuff' left on the sidewalk/ground/whatever, wash it away with water from the hose.
The delivery guy did you and himself a favor in my opinion. Survival of the fittest. Rattlesnake antivenom is really expensive. 10's of thousands of $$ out of pocket if your health insurance doesn't cover it.