[Barrett]

Thanks, gents, one & all.
Here's a bit of additional background.

Gontermann is credited with the 55th Cie. balloon on 8 Apr 17 though my source doesn't mention choice of weapons. However, French reports some attempted aerial bombings, to wit:

On 9 Feb a German aircraft destroyed the 72nd Cie balloon by bombing
On 23 April a Rumpler dropped two bombs on the 36th Cie. balloon without result
On 4 Sep the 48 Cie balloon was damaged by an aerial bomb

Incidentally, despite the obvious hazards, it appears that relatively aeronauts were KIA. The USAS lost just one observer and I can find fewer than 30 French fatalities, including accidents, 1916-18. Don't have much info on Brits, and German info is extremely thin. However, based on Allied claims, the Germans lost a hellacious number of Drachen in 1918; well over one a day from May onwards.