From the YouTube video description:
Los Angeles: On November 2, 2011, at around 11:40 p.m., Rampart Division officers responded to a radio call of an "Assault suspect armed with a gun" at a hotel located in the 300 block of N. Vermont Avenue. When the officer's arrived, they saw a man on the ground being held by two citizens.
Shortly before police arrived, the desk clerk at a local hotel took notice of a man with a back pack who walked into the lobby and began to suspiciously look around. He asked the clerk about the price of a room, and then pointed a gun at him and demanded money. The suspect walked around the counter where the clerk stood and told him to open the cash register. The clerk, fearing he was going to be shot, opened the register and gave the suspect money.
During the robbery, an elevator door opened, and two hotel guests who happened to be martial arts experts visiting Los Angeles from Oregon for a martial arts' tournament heard the clerk's cry for help and immediately took action. The pair grabbed the suspect who was holding a gun in his right hand. During the tussle with the suspect, the Good Samaritans repeatedly asked him to drop the gun and stop struggling. The pair was finally able to wrestle the gun from the suspect and took him to the ground with a leg sweep and then held him on the ground until Rampart Division officers arrived.
The suspect, identified as 31-year-old Luis Rosales, a resident of Los Angeles, was taken into custody without further incident. In addition, a loaded 9mm handgun and the money taken from the cash register were found inside Rosales' backpack. Rosales was booked for armed robbery with a firearm. His bail is set at $101,250.