Is it normal for these mood swing...?whats wrong?!

Okay so my dad has been like acting weird. She's been a painter/carpenter for pretty much his whole life. Like 25 yrs ago, he fell and injured part of his brain. He's kinda short tempered, which frightens me sometimes. But for this whole year he's been acting..different. He gets angry and overreacts alot, ie throwing a remote if it doesn't work, slamming doors, just easily angered. His painting business has been kinda slow for the past year, but not too bad, and he got out of back surgery mid feb., so he's had a legit reason to not go in. But he's been in a mad mood ever since he left the hospital, yelling alot more that usual, spending alot of time out driving, just abnormal stuff. is it normal for this to happen? What should I do? It's like really freaking me out!!