<human>: As some background: I am a 24 year old female working for a smallish, but well-known and well-regarded company where I live. What the company does is irrelevant for this post.

My boss has always been a dick. He is mean to all employees, yells when things that aren't that important are slightly off, and is a very dismissive person in general. I have never liked him, but today is the icing on the cake.

The boss often brings his older dog in to work with him. She is a sweet dog whom I pet often while working at my desk, and she loves attention. 

Today, I came in at my usual time. Shortly after I began work, the boss came in alone. I didn't think anything of it. On some level I thought to myself "oh he didn't bring his dog in today", but as I said I was not fazed. 

We started work at 7:30am.

3pm rolls around. He asks "Where did *dogs name* go?"

We all reply that we haven't seen the dog all day. He jokes that maybe she has been in the car all day. After which, he goes to check his car. 

Guess who left his dog in the car all day? 

I won't get into the specifics of the temperature, but needless to say, the dog died from the heat. 

I really liked that dog. She was super sweet and nice and getting old and she was a staple of the office.

I don't know what to do I just feel so completely sick to my stomach. I hate him so much for doing that to a poor animal who totally trusted him.

What planet is he living in where he can forget his dog is with him in his car? 

I get it that sometimes accidents happen, but with all of the other awful personality traits he has I just can't even stand to be in that office. The whole day felt like an eternity. 

Really I want to quit and get out of there. Another part of me obviously thinks that that is a rash and bad idea. I don't know what to do.

Can you summarize the given text in a few sentences?
<bot>: My boss left his dog in a hot car all day and she died. What do I do about my feelings of hatred towards him?