I live in the 18th quarter of Paris - the very northern tip of the city. When I moved into my apartment 5 years ago, I could heard firecrackers being set off at all hours of the night from mid-june to mid-August (the 14th of July is when we celebrate our independence day). Sometimes I think I heard gunshots too - rare for France but there were a few drug-slinging gangs in the neighborhood back then.
Every year it gets a bit calmer, and this year I only heard firecrackers on the 14th of July
I don't really get it, but I think it may be due to the drastic increase in cost of living in my neighborhood (40% in 5 years). The firecracker population gradually got pushed outside of the city limits..