Really liked the idea. I think the one thing holding the game back is that it was hard to control the security guards to react exactly how you wanted them to, while the robber was really fast so it didn't give you time to fiddle with positioning.
I think one thing that could have helped you is to separate the movement from turning, if you could give the guards a position, and then separately tell them which way to face, it could have made giving them exact orders a lot more fluent.
Anyway I enjoyed the game would love to see what you'll do with it with more levels and a tiny bit more polish!