How to transition right after the animation finishes for the first time.

Hello, Today's the first time I'm trying to use the Animator controller. I've managed to set up a transition triggered by a "trigger" which I set via script. That works. I want the second state to play an animation **once** and then return to the previous state. How do I accomplish this? I'm sure it's easy but I didn't manage to find anything useful in a few minutes of Googling. Thank you!