HF is damnasty stuff. It can kill you before you realize it. It does not give a burning sensation on contact, but will continue to eat away inside.
Prayers up for the driver and all others in the area, esp. police/EMS/Rescue/and fire/hazmat crews.
It'll turn your bones to Jello if you don't notice in time.
The fluoride will also pull the calcium out of your system and mess up your electrolyte balance and give you a heart attack.
The medical treatment is 1. calcium gluconate which ties up the fluoride and 2. debridement, that is, cut the dead skin off before the acid can burn any deeper.
I got the stuff on me once, only once. I was much more careful after that.