This documentary will more or less answer that question. They are mainly used as a distraction to hide the secret space program that has been happening for decades, since WWII.
Many of the "terrorist" "shootings" are planned and aided by a rogue faction operating within the government. This is the "covert" activity that John F Kennedy, Ted Gunderson, and others have spoke about. The "deep state" NWO government work very hard to create fear of guns which aids their agenda to disarm Americans.
Above Majestic Full Documentary
Here is more related information that you may want to see.
Zero Point Energy:
Phil Schneider talks about the Deep Underground Military Bases (DUMB's), grey aliens, and the NWO agenda:
Jim Marrs speaks about WWII and what he calls, The Fourth Reich:
Mark McCandlish talks about zero point energy, interstellar travel, and the alien reproduction vehicle (ARV) called the Fluxliner:
William Tompkins talks with Kerry Cassidy of Project Camelot and Michael Schratt about the secret space program and black projects:
See more in the video below about the Fluxliner and probable tech and hardware that the US military and aerospace industry are using to explore space. This Fluxliner craft is old tech and hardware by todays standards since it was spotted at an air show back in 1988.
Now remember, in 1988 the US Air force were understanding that the SR71 Blackbird was somewhat obsolete, expensive to fly and not so practical with it having such a wide turning radius and complex flight procedure, thus it was retired in 1990. Something to keep in mind before you dismiss this "Fluxliner" as being impossible.
Also to consider is the fact that the aerospace industry faded out of the spotlight over the years as Hollywood and the mainstream media increased their fear porn and distractions on the public.
Hollywood, "reality" shows, sports, consumerism, scandals, all provided the distraction needed to hide the giant leaps in tech and hardware advancement in the aerospace industry, most of which could not be shared with the public due to security reasons. It's now 2020 and the public are surprised by this sort of actual real news, and people behave as if the tech is not possible. HA! Ignorance is not bliss. Don't be so naive. Take up physics and chemistry, and then you will understand the magnitude of the aero-space- industry. It's beyond the comprehension of many but that doesn't mean that the reality does not exist for other people.
If you are still seeking more information, Al Bielek in the following video speaks about a number of fascinating topics including time travel using Nikola Tesla tech, WWII and Hitler, Dracos, etc.
Last but certainly not least, Emery Smith speaks with David Wilcock about his high profile career performing autopsies on numerous species of aliens:
John Lear speaks about the civilization on the Moon, and on Mars, with related content: