I'm new and somewhat stuck...

I've accepted an assassination-task and the objective changed, offering me a higher payout, I accepted that and killed the original target, as it pulled me out of hyperdrive while accepting the other task anyways, so far so good.

Now I still have the Task on my Left-Hand Panel, telling me to kill that other Target in a different System. I've travelled there and received a new mission marker, and this is the point I'm stuck at...

I'm now at the mission location, and there is an System Authority Vessel, which was displayed "Green" as I scanned it, but I just can't find my actual target. I see the target chatting, being afraid of being caught as an Informant, but I can't see his ship.

I'm confused, what am I doing wrong? I've out of frustration and not being able to resolve that situation on my own thought that attacking that Authority Vessel was a clever idea, leaving me with a bounty and the mission not being complete.

Screenshots after cruising away and back to the mission (Album): https://imgur.com/a/p2clrWH

Another thing I didn't understand, why did I get a bounty, I thought "system link error security response unavailable" means that I won't get a punished for unlawful actions?