Why?

Why is he such an angry person? I called my dad to ask if my brother and sister were going to the family Easter egg hunt, then asked if he was going to church tomorrow morning. He got all upset and told me he couldn't answer any questions cause he was shopping. Naturally, him being angry with me was upsetting. So I left the room.
Then, my grandpa goes behind my back and calls my dad to get on to him for making me upset, saying that he was being mean.
Of course, I never said Daddy was mean, just angry. So then, he calls me, getting mad that I said he was mean and that I was upset. I tried to calm down enough to tell him that I never said he was mean, just that he sounded upset. So he starts semi-yelling at me, saying that he wasn't mad. I'm sorry, but generally when someone's yelling at me, it leads me to believe that they're angry.

And the thing is...he's always like that. He's alwasy so angry.
I just want to know what I did to make him so mad...