Hezbollah is the main political party in Lebanon. Anything can be related to the main political party of a country. It's like saying you can legally kill Israeli medics because they are "related to Likud".

In any case, killing medics is a violation of the Hague and Geneva conventions and the internal law.

If this story is hard for you to take seriously, there's thousands more stories, videos and witnessings of war crimes by Israel in very recent history..

What does it mean for a medic to “be Hezbollah” in this context?

Are you saying they are employed medics of the organisation? Party members? Combatants?