Now, video released Arpaio's office shows it was one of his men, not any of the Phoenix police officers, who used the Taser to try to subdue Atencio.
The veteran was taken to a Phoenix hospital after the scuffle. There, he was pronounced brain dead and kept on life support for days. On Tuesday, his family gathered by his bedside and gave doctors the order to remove him. He died a short time later.
The video released Friday was made available on DVDs to local media outlets in Arizona. The footage showed the altercation from 26 camera angles. The struggle took place in the early hours of Dec. 16 inside a Maricopa County jail and came just hours after the Justice Department accused Arpaio's agency of routinely violating the civil rights of Latinos.
Along with the footage, the sheriff's office also released a statement and partial timeline of the altercation. The agency sent both to TPM.
The timeline said Atencio was brought to the jail at about 1 a.m. by Phoenix police, who had arrested him earlier on suspicion of assault.
The Phoenix officers began to have problems with him at 1:11 a.m., but the real trouble began at 2:34 a.m., near the end of the booking process. The sheriff's timeline said that's when a "physical altercation" with Phoenix police officers ensued.
An excerpt of video, broadcast by Phoenix TV station KPNX and embedded below, shows Atencio talking to officers, then folding his arms and backing up against a wall. Officers then grabbed him and began to wrestle him to the ground. At least 10 officers combined from both agencies can be seen in the room.
Two minutes into the struggle, according to the sheriff's timeline, a Maricopa County detention officer used a Taser on Atencio "in order to gain compliance." Arpaio's office did not release the name of the officer.
Atencio was apparently subdued by the electric shock, but the sheriff's office said he was still conscious and making comments about killing himself after that.
Because of the comments, the sheriff's office said Atencio was searched, stripped and put into a "safe cell" at 2:41 a.m. The agency said he continued to talk as officers and medical staff left the cell.
The video, however, shows that Atencio remained on the floor in the same position they left him for the next 11 minutes.
When medical staff checked on Atencio again at 2:52 a.m., they found he was unresponsive and began using CPR and other methods to try to keep him alive. He was later taken to St. Josephs Hospital and Medical Center in Phoenix in critical condition.
Before the video was released on Friday, an attorney for Atencio's family, said they had no plans to comment on it until next week.
"They are deeply grieving the death of their Marty and do not want their burden and hurt to further interfere with the joys, blessings, and good cheer that other (Phoenix area) families are looking forward to on this eve of the Christmas weekend," attorney Mike Manning said in an email. "We will have a comment on Monday or Tuesday."
Manning previously questioned why it had taken so long for the sheriff's office to release the footage.
"We're concerned about it being destroyed. Because that's what the sheriff's office always does in cases like this," Manning said earlier this week. "We want that digital video released right away."
He also said many of Atencio's bizarre actions could be explained by the fact that the veteran suffers from bipolar disorder and was off his medication. Doctors at the hospital found no drugs or alcohol in his system, Manning said.
The sheriff's office declined to comment further and did not explain why it took a week after the altercation to release the video.
Joel Robbins, another prominent Phoenix attorney, watched the video and told KPNX it raises a lot of questions about the officers' use of force.
"He may have been loud. He may not have sat down when he was asked to sit down," Robbins said. "But nothing in this video has shown me any danger to the officers that justified deadly force."
The video from KPNX is below.