The terrifying future we see in the Terminator movies is not that far-fetched, according to Tesla CEO Elon Musk. While speaking at a technology summit, the entrepreneur warned that governments should invest in artificial intelligence regulation.

“I have exposure to the very cutting edge AI, and I think people should be really concerned about it,” Musk told the National Governors Association summer meeting on Saturday. “I keep sounding the alarm bell, but until people see robots going down the street killing people, they don’t know how to react, because it seems so ethereal.”

Musk says the solution to rapid advances in AI is proactive regulation, which would mean implementing limits to how quickly companies can develop new systems before “a whole bunch of bad things happen.” Musk is usually against this sort of regulation, but since AI concerns a “fundamental threat to human existence,” he is more concerned than ever.

“AI is a rare case where we need to be proactive about regulation instead of reactive. Because I think by the time we are reactive in AI regulation, it’s too late,” he said.

Musk is not alone in his opinions, but he is one of the few vocal opponents of advances in AI technology. You can watch his interview in full below, with his remarks on AI starting at around 48 minutes: