He also was charged with receiving stolen property for picking up a stolen gun, which is a second-degree felony.
The other teen, who was witness to the shooting and allegedly brought the gun to the party in the first place, was charged with reckless endangerment, also a class A misdemeanor, and second-degree felony receiving stolen property.
That boy told police he got the gun from "a kid" who purportedly stole from a home, according to charging documents.
Police confirmed the gun had been stolen from a Cottonwood Heights home on May 24, the documents state.
Less than two weeks later, it was in the hands of three teenage boys in a basement near 6800 South and Pine Rock Drive (3030 East).
The three boys were joined by two girls, who allegedly went to the home to celebrate the end of school, and so the boy who received the gun could show it off, according to charges.
It was his birthday present, he said.
The three boys went into a closet to admire the revolver. As they passed the weapon around, the boys told police, they didn't know it was fully loaded.
The gun went off, and a bullet hit Jarrett in the head.
Both teens implicated in the shooting have remained in juvenile detention since the incident.
The boys are not being named by The Tribune because they are juveniles.
A third person was also arrested and detained in connection with the residential burglary during which the gun was taken, Cottonwood Heights police confirmed Monday.
Police said the heist included several firearms, including the weapon that killed Jarrett a .45-caliber revolver.
Jarrett's grandmother, Lisa Baxter, reportedly had said that the shooting was an accident, and Jarrett wouldn't want charges filed against his two Brighton High School classmates.
A fund has been set up at Wells Fargo Bank under Harley Jarrett's name to help with funeral and other expenses.
Twitter: @remims, @Marissa_Jae