This is a common issue that crops up, it's because several animation events are true at the same time. For example in your screenshot, pressing S to shoot, at the same time if you are standing still also the 'stand' event is true of speed = 0, so it is trying to play 'stand' and 'shoot'. You are approaching it correctly with the conditions for the player but you need to try (in as non-convoluted way as possible) to make sure more than one scenario cannot be true. For example you would add to stand event 'is not shooting' or 'S is not held down', but you need to make sure it is as easy to follow as possible :)