"Soon" and "early" are similar, but they measure time from different points.
"Soon" measures the time after something. That can be after now:
I'm leaving soon.
Or it can be after a point in the past, like the point when the employee noticed that there would be a problem:
Why didn't you tell me about this sooner?
"Early" measures the time before something, like before now or before the time when something is going to start:
Let's go. I want to get there early.