The world's leading artificial intelligence experts are sounding the alarm on killer robots. Tesla (TSLA) boss Elon Musk is among a group of 116 founders of robotics and artificial intelligence companies who are calling on the United Nations to ban autonomous weapons. "Lethal autonomous weapons threaten to become the third revolution in warfare. Once developed, they will permit armed conflict to be fought at a scale greater than ever, and at timescales faster than humans can comprehend," the experts warn in an open letter released Monday. "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 says.