In this case, much depends upon the context.
Since we don't have much more, we cannot determine whether "boss" or "employer" will work better here. Either could be appropriate, depending upon the circumstance.
I'm not sure perpetrator is exacly right, unless this were, for example, a hit and run, or drunk driving, accident, where the one who caused the accident actually committed a crime.
Instigator might work, but its more frequent use is that of someone who deliberately stirs up or starts trouble.
Without further context, it's hard to tell. Perhaps tievoli can provide us with a sentence or something that would help us find the appropriate word(s).