As the world’s most powerful computer systems begin to embrace artificial intelligence in earnest, using smart algorithms to increase efficiency and and speed, the potential damage that a “rogue” AI could cause continues to grow. Many in the tech community have theorized how an artificial mind could turn against its creators, and Facebook just got an interesting lesson in how such a scenario might unfold. Facebook engineers were forced to pull the plug on one of the company’s AI systems after its bots began communicating with each other in a completely new language which humans simply couldn’t decipher.

The AI bots, which were originally programmed to use plain english to communicate with one another, were found to be speaking what appeared to be gibberish. Sentences like “I can can I I everything else” and “Balls have zero to me to me to me to me to me to me to me to me to,” were being sent back and forth by the AI, and while humans have absolutely no idea what it means, the bots fully understood each other. Without being able to understand how or why the bots were communicating, Facebook had no choice but to shut down the system.

The very obvious danger here is that computer which can communicate with each other using their own language are not only impossible to understand but much more difficult to control. In this case, the bots were not bound by plain language and seemingly developed a more efficient way of communicating with each other, deciding for themselves what was best. It’s both impressive and scary.

Facebook’s Mark Zuckerberg is a huge proponent of artificial intelligence, and has even clashed with other tech leaders like Elon Musk over his embrace of AI and apparent lack of concern over the theoretical dangers intelligent computers could pose to humanity. After the events of this weekend, perhaps he’ll change his tune a bit.