Following the December 2015 terrorist attack in San Bernardino, California, in which 14 people were killed by Rizwan Farook and Tashfeen Malik, the Federal Bureau of Investigation solicited Apple to assist in "unlock[ing]" an iPhone 5C used by Farook. On February 16, 2016, in response to a request by the Department of Justice, a federal magistrate judge ordered Apple to create a custom iOS firmware version that would allow investigators to circumvent the phone's security features. Cook responded in an open letter, wherein he denounced the government's demands as constituting a "breach of privacy" with "chilling" consequences.