The police department announced on Twitter Thursday that officer Jaron Jones "tendered his resignation." Jones had been with the department since October 2016.
"Jones was one of the employees involved and depicted in the photograph investigation related to #ElijahMcClain. We will continue to update w/developments as we proceed," the tweet read.
Jones and multiple officers from the Aurora Police Department were placed on paid leave after the allegations were reported to internal affairs last week.
Aurora police interim chief Vanessa Wilson did not provide details about the pictures and did not say where they were taken.
"I immediately ordered Internal Affairs to make this investigation their top priority," Wilson said in a statement. "This accelerated investigation was completed this evening."
Wilson said that the investigation, which included reports and photographic evidence, "will be publicly released in its entirety promptly upon its conclusion."
McClain, a 23-year-old Black man, was stopped by police last August after someone reported seeing a suspicious person wearing a mask. Officers put him in a chokehold and McClain went into cardiac arrest. He died at the hospital after he was taken off life support.
The three officers involved in his death were moved to "non-enforcement" duties.
Video shows that McClain, who was wearing a ski mask, had bought iced tea at a convenience store and was walking down the street when he was stopped by the officers. He's heard on the video telling them that he's an introvert and was heading home.
McClain's family has said that he often wore a ski mask when he felt cold.
A confrontation ensues as the officers appear to wrestle McClain to the ground. He is heard on the video telling police that he "can't breathe correctly."
He suffered cardiac arrest on the way to the hospital after paramedics administered a sedative to calm him. McClain's death was due to "undetermined causes," a coroner said.
The coroner did not rule out whether the police chokehold, in addition to the sedative, might have contributed to the death.
Police said in a statement at the time that "the male would not stop walking down the street from the officer" and "resisted contact, a struggle ensued, and he was taken into custody."