New Delhi, Feb. 23 -- School was canceled in several Mexican states and local and foreign governments alike warned their citizens to stay inside, as widespread violence erupted following the army's killing of the powerful leader of the Jalisco New Generation Cartel.

Nemesio Ruben Oseguera Cervantes, known as "El Mencho" was the boss of one of the fastest-growing criminal networks in Mexico, notorious for trafficking fentanyl, methamphetamine and cocaine to the United States and staging brazen attacks against government officials who challenged it.

He was killed during a shoot-out in his home state of Jalisco as the Mexican military attempted to capture him. Cartel members responded with violence across the country, blocking roads and se...