IANAL but I am a CCW holder which makes me a member of a most law-abiding population. I am also a pilot and as such have read up upon and internalized much of the relevant FARs (Federal Air Regulations) applicable to GA (General Aviation) flight. The link has always been there on the left sidebar "FARs, direct from HQ".
Off the top of my head, It seems there are two relevant FARs: 91.15 (Dropping objects):
§91.15 Dropping objects.Now I am but a mere pilot and not a lawyer, Even assuming the guy controlling the drone is PIC, it seems to me the craft was well controlled and firing into a berm so it would seem to me "reasonable precautions were taken to avoid injury etc....". Sorry no sale if I'm on the jury.
No pilot in command of a civil aircraft may allow any object to be dropped from that aircraft in flight that creates a hazard to persons or property. However, this section does not prohibit the dropping of any object if reasonable precautions are taken to avoid injury or damage to persons or property.
But there is also the catchall 91.13 "Careless or reckless":
§91.13 Careless or reckless operation.This is pretty much the FAA's "you are guilty if we deem you so". Except, is a drone in this situation engaged in air navigation (case a)? It would seem to me not the case. Nor would (case b) seem to fit as the scene could hardly be described as an airport.
(a) Aircraft operations for the purpose of air navigation. No person may operate an aircraft in a careless or reckless manner so as to endanger the life or property of another.
(b) Aircraft operations other than for the purpose of air navigation. No person may operate an aircraft, other than for the purpose of air navigation, on any part of the surface of an airport used by aircraft for air commerce (including areas used by those aircraft for receiving or discharging persons or cargo), in a careless or reckless manner so as to endanger the life or property of another.
This is truly a case of technology outpacing legislation. I have great faith our vast army of FAA bureaucrats will write new rules making the arming of drones illegal. But as of today, I don't think that is the case. And.. umm insert legal doctrine "ex-post-facto" means they can't prosecute someone for an act today that wasn't illegal until tomorrow (or increase penalties in the same situation).
I also have great faith criminals with no concern about our laws will make great use of same-same technology to complete their missions. Yet again proving laws only stop the law abiding, not the criminals.
Clearly the technology is out there, Security has to react assuming the worst. Making it illegal doesn't stop the threat.
Others have brought up the "machine operated gun angle" (does firing a gun from a computer operated solenoid make it a "machine gun"?) I have no knowledge or opinion on that side.