I just got fired.

[WingedWolfPsion]

I don't understand. This was my first volunteer job. I don't know what I did wrong but I know I need to learn fast.
Please help. I'm really kind of crushed inside, despite the anger. I was there for the animals, not the clients, and I got fired for something that had to do with the clients and what happened in the lobby.
I wanted to help and I got rejected.

Well, if it were an actual job, the absences so early on would have been an issue. As it is, I think the most important thing you have learned from this is something you would, unfortunately, have learned sooner or later anyhow--there are some seriously ffed up people who run businesses, and if your employer is a nutcase, there is really nothing you can do about it other than move on.
You probably should not tell a client at a vet office that your dog was put down...that's a bit of a scary downer for them, lol. They want to hear something reassuring.

I think the folks you were volunteering for were just bonkers, though, or they would have helped you out, rather than behaving the way they did. "Don't talk to clients"? Seriously? 0_o