LAS VEGAS (FOX5) — A security guard shot a kitchen employee in the chest at Atomic Golf and barricaded himself inside an office for six hours before surrendering to police.
Andrew Mullen was arrested at 3:27 p.m. on Saturday at Atomic Golf and faces charges of battery with a deadly weapon, discharging a firearm within an occupied structure and resisting a public officer with a firearm.
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Regla Martinez-Masso was shot in the upper left chest around 8:13 a.m. while working on the second floor of the facility. She was transported to University Medical Center and treated for her injuries.
The shooting
Martinez-Masso, a kitchen cleaner, arrived at work between 7 a.m. and 7:30 a.m. She was in the employee breakroom on the second floor when she heard a male voice yell “open the door” in English.
Coworker Daisy Silva encouraged Martinez-Masso to open the door leading to a hallway where the executive chef’s office is located. When Martinez-Masso opened the door, she was struck in the chest by gunfire that came through the wall.
Silva said she heard one shot and saw a hole in Martinez-Masso’s zip-up hoodie with blood on her chest. The two women ran downstairs and escaped the building.
The barricade
Mullen barricaded himself inside the chef’s office using furniture. The Las Vegas Metropolitan Police Department SWAT Team and Crisis Negotiators Team responded to the scene.
Crisis negotiators accessed live video surveillance and identified Mullen as an employee who worked as an armed security guard. Negotiators contacted Mullen’s wife, Andrea Mullen, who confirmed the man inside was her husband.
Mullen remained barricaded for approximately six hours while armed with a revolver before surrendering to officers.
The investigation
Video surveillance captured Mullen entering the chef’s office at 8 a.m. wearing his security shirt with no shoes on. He waved at the camera and showed he was armed with a revolver.
Mullen fired two rounds through a window connecting the office to the employee breakroom at 8:07 a.m. He fired additional rounds at 8:07 a.m. and 8:08 a.m.
At 8:13 a.m., Mullen fired the round that struck Martinez-Masso in the chest as she stood on the other side of the wall in the breakroom. He then barricaded the door with furniture.
Detectives recovered 11 spent cartridge cases throughout the offices and a speedloader containing four cartridges.
Suspect interview
Mullen told detectives he has been diagnosed with PTSD through the Veterans Affairs. He served in the Army for five years in infantry.
Mullen said he began working with Magana Security in November 2025 and was assigned to Atomic Golf.
He worked Thursday through Sunday from 10 p.m. to 6 a.m., and Mondays and Tuesdays from 2 p.m. to 10 p.m.
Mullen said he carried a .38 Special revolver with a five-round cylinder and brought two extra fully loaded cylinders for a total of 15 bullets. He admitted he discharged his revolver 12 times during his shift and had three bullets remaining when he surrendered.
Mullen said he became paranoid that “Hispanics were going to harm him.” He said he sprayed mace on the floor to keep people away and turned up the volume on a television to cover the sound of his footsteps. He removed his shoes and took a position in the chef’s office.
Mullen said he saw movement through holes in a darkened window and shot at the movement. He said he later learned while being taken into custody that he shot a woman.
Mullen’s wife told detectives he left their residence in an agitated state and said people had been trying to break in. He told her to call for help if she did not hear from him in 25 minutes.
Mullen is being held on $35,000 bail.
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