LOS ANGELES (CBSLA) – A Utah man suspected of both gunning down an off-duty Los Angeles County sheriff’s deputy in an Alhambra Jack in the Box, and a Russian man in a drive-by shooting in downtown L.A. – just one hour apart — pleaded not guilty Monday to double murder charges.

Rhett McKenzie Nelson is suspected of killing an off-duty LASD deputy and a Russian man just an hour apart.

Rhett McKenzie Nelson, 30, was arraigned in L.A. County Superior Court, where he plead not guilty and was ordered to remain jailed without bail.

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Both murders occurred on the evening of June 10. Prosecutors allege Nelson shot 50-year-old Deputy Joseph Gilbert Solano after killing 31-year-old Dmitry Alekseyevich Kolstov, an accomplished skateboarder and snowboarder from Russia.

Authorities believe that after killing Solano, Nelson committed two armed robberies in Long Beach. One happened at a Shell gas station and the second at a 7-Eleven. He is also accused of attempting to murder a third person that same day.

Solano, off-duty and in civilian clothes, was ordering food shortly before 6 p.m. on June 10 at a Jack in the Box at 2531 W Valley Blvd. in Alhambra when a man walked up behind him brandishing a handgun and shot him in the back of the head, according to the sheriff’s department. He passed away two days later.

Kolstov was shot about an hour earlier in the 1900 block of East Seventh Place, between Santa Fe Avenue and Alameda Street. Friends told the Los Angeles Times that Kolstov was hopping off a board and with a group of other skaters when the shooter drove toward them in a Kia Sorento.

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Los Angeles police Chief Michel Moore said the shooting was carried out by a gunman in a white SUV matching the description of Nelson’s Sorento, which was also spotted at the scene of Solano’s shooting. Moore said Kolstov was standing in the area when the SUV pulled up and there was some type of verbal exchange, ending with the shooting.

Nelson was arrested the day after the killing, June 11, after he was spotted in Long Beach.

San Diego police, meanwhile, say Nelson may also be a suspect in five armed robberies and attempted armed robberies that took place from June 7-9 in that area.

Nelson’s family in Utah reported him missing in late May and noted he has a history of opiate abuse. Nelson had a misdemeanor drug conviction in Salt Lake City in December 2014, but no other criminal history. His father is a prominent doctor.

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(© Copyright 2019 CBS Broadcasting Inc. All Rights Reserved. City News Service contributed to this report.)