You can test what animation is currently playing and set bullet angle to that animation
if "walk left" is playing set bullet anggle to 0
if "walk down"... set to 90
or you can name your animations to 0 - for walk left, 90 - for walk down... and then set bullet angle to animation name
there's quite many ways to go with what you want to do.
Best way is to put your capx file here and ask to look at it and help you with events you already have.