Not making any excuses for what has happened in Nanterre, but just to add a bit of context, I note that in 2018 ( just 12 months ), 25 Police officers and gendarmes were killed in the line of duty. I'm not aware of recent statistics.
Ah....Belgium.......and in particular the wonderful city of Brussels. That hot bed quartier, that has bred so many terrorists and murderers. Who would have thunk it...?