Absolutely not joking. Only a psychopath can kill someone then go about their day as if nothing happened. No remorse what so ever.
Absurd.
First of all you have to keep in mind that, if his story is true, he believed he'd acted in self-defense. So he didn't think he had anything to feel bad about.
Secondly, depending on when he ordered the pizza, we don't know if he'd seen anything on the news yet indicating that someone had died.
Btw, do we know it was him who called the pizza place, vs. his gf doing so?
Thirdly... a lot of people don't seem to understand just how strange it can be to be in that situation, if it's completely foreign to you you imagine it to be some thing that completely makes the universe hit the pause button... but everyone reacts differently in crazy situations, and a lot of people, probably MOST people, still go on about doing normal things... if they have to pee, they pee, if they are hungry, they eat.
You think he should have curled up in the fetal position on the hotel bed and wept? Or what?
Until you're in a situation like that, you just can't say how you'll act.
The adrenaline, the over-thinking of everything, questioning yourself and your actions, processing what happened... they can leave you stunned, and it can trigger your mind to go on a sort of auto-pilot and do what's familiar.