An international effort from leaders in technology and artificial intelligence (AI) spearheaded by Elon Musk is calling on the United Nations to take proactive measures against the spread of future lethal autonomous technology: killer robots.

The open letter signed by over 100 industry leaders to include the renowned CEO of Tesla and SpaceX cites the threat of “Lethal Autonomous Weapon Systems” as the “third revolution in warfare,” following gunpowder and nuclear weapons, that will “permit armed conflict to be fought at a scale greater than ever, and at timescales faster than humans can comprehend.”

“These can be weapons of terror, weapons that despots and terrorists use against innocent populations, and weapons hacked to behave in undesirable ways.”

The letter ends with an ominous warning: “We do not have long to act. Once this Pandora’s box is opened, it will be hard to close.”

As it stands, the United Nations has established a Group of Governmental Experts (GGE) on Lethal Autonomous Weapon Systems within the UN’s Convention on Certain Conventional Weapons. There are no specifics on how the UN should proceed with the initiative in the letter, only encouragement to “work hard at finding means to prevent an arms race in these weapons.”

Musk has long warned against the threat posed by artificial intelligence. In 2014, he called it mankind’s “biggest existential threat.” Many technology leaders believe AI will not only improve our day-to-day lives by making certain tasks easier, but will have a similar effect on warfare.

For example, a group or nation which possesses the ability to launch autonomous drones against a rival or enemy that does not possess a similar capability will face much less risk, and thereby be encouraged to initiate hostilities.

The doomsday scenarios are easy to imagine. Automated, industrialized warfare has long been prophesied as a dystopian future in literature and movies, where in the ultimate irony, machines built by man to make life easier, cause man to face extinction at the hands of his creations.