I wonder what kind of acid he got. I'm guessing either sulfuric acid or nitric acid. Both are easy to get/make. Nitric acid works much faster than sulfuric acid, but both will do terrible damage pretty fast.
I got a drop of sulfuric acid on my arm once without knowing it, but I knew it in about five seconds. It began burning, then stinging. I quickly ran to the bathroom and washed it off, and even though it was only on my skin for about 15 seconds it left a red, badly swollen spot on my arm. But that healed pretty fast.
I also accidentally splashed niric acid on my ankle. it went through my sock and immediately, I'm talking less than a second, began burning like crazy. Within less than 8 seconds I had it completely washed off (I was next to a hose), but it deeply burned a few small spots. Six months afterwords, the three little red scars, about a half a centimeter in diameter each, are very easily visible.
If I had to choose, I'd chose sulfuric for this guy. It works slower.
EDITED TO CHANGE "new" TO "knew"