Michael Edward Abeyta, 47, is accused of unlawfully carrying a weapon at a "No Kings" anti-Trump protest in El Paso.

In a city notorious for unruly crowds at large sporting events, protesters were peaceful and law-abiding — as were the police.

Detectives don’t yet know why the alleged rifleman pulled out a weapon or ran from the peacekeepers, but they charged him with murder and accused him of creating the dangerous situation that led to A...