A Laramie County Circuit Court judge has dismissed the charges against a 21-year-old Cheyenne man accused of shooting a 19-year-old man in the head and dumping his body in a reservoir on the Wyoming Hereford Ranch.

Armando Ramirez-Serna was facing charges of first-degree murder, aggravated robbery with a deadly weapon, first-degree arson and concealing a felony in the death of Justin Robinson, but Judge Denise Nau on Tuesday dismissed the charges.

According to an affidavit, Ramirez-Serna allegedly shot Robinson in the 7600 block of Braehill Road on Nov. 26 after trying to rob him of a pound of marijuana.

He then reportedly texted 17-year-old Angelo Trujillo, who allegedly drove with him to the 5300 block of Burlington Trail Road and helped him burn Robinson's SUV and dispose of his body.

"It's clear from the evidence that Mr. Ramirez-Serna killed Mr. Robinson," said Nau. "(But) they are not these four crimes."

Nau said that there was little to no evidence of a robbery or that the shooting occurred during the robbery, a requirement for the first-degree murder charge to stick.

She also said there was no probable cause for first-degree arson or concealing a felony because Robinson's body was not in the SUV when it was torched and was spotted floating in the reservoir.

Laramie County District Attorney Jeremiah Sandburg says he was "a little shocked" that Nau dismissed all four charges, but wasted no time in filing new charges in the case, which included first-degree murder, third-degree arson and attempted robbery.

Ramirez-Serna will likely make his initial court appearance on those charges Wednesday.