Updated: 8:28 PM MST May 9, 2021 PHOENIX — An armed security guard fatally shot a patron overnight Sunday after an argument violently escalated. Police received reports of a shooting near 27th Avenue and Bethany Home around 1:37 a.m. When firefighters arrived, they found 29-year-old Ruben Sekiseka on the ground with a gunshot wound. He was later pronounced dead. Investigators learned that Sekiseka got into an argument with 34-year old Serafin Chavez, a security guard at a nearby business. Chavez told police that Sekiseka accidentally shot himself as he was escorted out of the business. But investigators say, they determined that Chavez was the one who shot him and then hid the bullet casing.