Mexico’s foreign minister is flying to Cairo after Egyptian security forces mistakenly killed 12 people when they attacked a group of Mexican tourists. Egypt’s Interior Ministry said the crew of an Apache helicopter opened fire on the tourists after mistaking them for Islamist militants. Mexican President Enrique Peña Nieto demanded an explanation Monday.

President Enrique Peña Nieto: “Yesterday’s events have saddened us as a nation. There hasn’t been a precedent in years of an event like this against our citizens. Mexico has demanded from the Egyptian government an exhaustive, thorough and prompt investigation which establishes responsibility.”