"Mr. Salgodo turned and attempted to grab the gun from Mr. Alvarez and during the struggle for the gun it went off, killing Mr. Salgado," the plea document states.
But according to charges filed in January, the girlfriend told police that she and Salgado had arranged to sell a PlayStation 4 via an online advertisement.
Alvarez's defense attorney, Michael Misner, said Tuesday that "Playstation 4" was code for drugs, in this case, marijuana.
Salt Lake County District Attorney Chief Deputy Jeff Hall said Tuesday that prosecutors didn't know when they filed the charges that drugs were involved, so it wasn't mentioned in those documents.
Salgado and his girlfriend drove to a Salt Lake County address to meet the Playstation buyers, Alvarez and 18-year-old Anthony Glen Taylor. The two men got into the back seat of the car, then said they needed to go to another location to get money for the purchase, charges state.
When they got to the Browning Avenue location, the two men told Salgado to pull over and Alavarez pointed a firearm at Salgado and announced it was a robbery, charges state.
After Salgado was shot, Taylor dragged the girlfriend from the car, hit her with brass knuckles, knocked her to the ground and then kicked her, charges state.
The girlfriend claims Alvarez pointed the gun at her. But in the plea document, Alvarez admitted only to pointing the gun at a woman motorist who stopped to ask if they needed help.
Alvarez and Taylor then fled on foot, taking property that may have included a Playstation 4 box, Misner said.
Police found Salgado dead in his car from a gunshot wound to the chest. No drugs were found at the scene.
A police search of the car revealed that Alvarez had left his wallet — containing identification and financial cards — on the backseat floor, charges state. He was arrested that day at his girlfriend's home.
Alvarez, who also pleaded guilty to third-degree felony aggravated assault, is expected to be sentenced to prison for up to life at a hearing set for June 2 before Judge Vernice Trease, according to the plea document.
Taylor turned himself into police the day after the shooting, charges state.
Charged with aggravated murder, aggravated robbery and other counts, Taylor is scheduled for a preliminary hearing on Tuesday.