Baron 1 hit KO

So baron just 1 shot me with his spit attack.

I was Braum, had sightstone sunfire warmogs, was at ~70% health. Baron went to use his spit thing with windup? (the AOE one with the charge time and prehitbox indicator.) I tried to put my shield up right about when he was going to do it, and instantly died. I tried to screen cap the death recap, but I think it said I took 67% from spit and 33% from basic attack.