Propofol stings too, but thiopental doesn't. I use STP for almost all of my pediatric IV inductions. Archaic but useful drug.
I'd guess the ER used etomidate for the induction in that case because that's all the ER ever uses for any induction in anyone. 🙂
As for the ER using etomidate for sedation ... there was a long contentious thread (aren't they all) in here a while ago about this. Some places apparently have credentialing policies where using propofol for sedation requires the anesthesiology department to be involved. Some ERs get around that by using "their" drug, etomidate. Also, it's harder to hurt someone right away (hemodynamically speaking) with etomidate than propofol. I've never seen an ER doc push phenylephrine or ephedrine; they use pressors the way the ICU uses pressors: call up the pharmacy and start a drip when it gets there. Not so great if you've just bottomed someone out with propofol. I can see why the ER likes etomidate ... it's a safe stable drug for the next 30 minutes, and the adrenal suppression (if it happens) will be handled down the road by someone else.