The people on the stage and later the troops on the ground that broke ranks and scattered did not seem to be reacting to any event in their local area, like a drone crashing to the ground or such. They just panicked.
Maduro sounds like a drone himself, btw.
Actually, I have done a lot of translating about Latin American guerrilla bands (FARC,etc) and the propane tank was a weapon of choice. The tanks are used for cooking throughout Latin America so they’re easy to come by. They’d put them onto a launcher and send them at a target (a military unit, a police car or a just a private house) and, while they couldn’t go enormously far and weren’t enormously accurate, they blew up and did the job.
I doubt that this was a drone, because they’re pretty accurate, and in any case, they’re hard to see. The soldiers were running because they saw something and they were running away from where they thought it would land.
It looks to me as if the tank overshot and crashed into a building before it exploded. Or those photos may simply have been of the place from which it was launched and it failed to explode at all.