Explosive means of communication

So six Israeli fighter planes overflew a vessel of the German navy which is part of the UNIFIL mission to control Lebanon's waters and apparently fired two shots and/or flares. First the IDF denied the incident but by now the first reports seem to be valid and: As the ship "Alster" is a so called "fleet service vessel", the Bundeswehr-Dubbing for a spy ship, there is a video of the situation which has not been published so far.

But apart from the media impact which is somewhat dampened by public attention being drawn to pictures of German soldiers posing with skulls in Afghanistan, the reasons of this incident remain interesting.

So... What the hell was this supposed to mean?

My guess is that someone in the IDF wanted to show UNIFIL who is really in charge, but this sabre-rattling gesture backfired massively, although the German and Israeli governments tried to downplay the situation. And viewed in combination with the French force commander's complaints about Israeli fighters patroling southern Lebanon and his threat to station anti-aircraft-systems to defend his ground troops, the situation becomes somewhat to explosive. And this is definitely not the best way of communication between allies.