LOS MOCHIS, Mexico — At 4:40 a.m. in a central neighborhood of the Pacific coast city of Los Mochis, 17 Mexican marines began their assault on a safe house, thinking there was a good chance Joaquin “El Chapo” Guzman was inside. The operation was dubbed “black swan.”

One marine was wounded by gunfire almost immediately and remained outside the front door while his comrades slowly advanced inside behind lobbed grenades and heavy fire, according to video from the marines’ helmet cameras released by Mexico’s government on Monday.

A marine involved in the assault who gave a tour of the house to a reporter from the Mexican network Televisa said there were more people inside than expected and they were more heavily armed, including with rocket-propelled grenades and .50 caliber sniper rifles.

Attorney General Arely Gomez told local radio that people in the house had ordered food for 13 people the night before the raid.