According to a probable cause statement, Sloop assaulted the deputy on Nov. 21 just after 1 p.m. after refusing an order to return to his cell.
Sloop is accused of punching the deputy in the face twice, then attempted to gouge out the deputy's left eye with his thumb.
A second deputy went to Sloop's cell to assist, according to the probable cause, and tried to restrain Sloop.
But Sloop continued to strike the first deputy in the head, and then lunged up and bit into the deputy's thumb, according to the probable cause statement.
"As the inmate was being restrained, [Sloop] said, 'You f-er, I gouged your eyes,' and 'Davis, you fat f-, you are next, your turn is coming,'" according to the probable cause statement.
Sloop "attempted to bite through the deputy's thumb, causing a deep wound that required multi-layer sutures," according to charging documents.
"We think it's pretty serious," Deputy Davis County Attorney Steve Major said of the assault outside of court Friday. "That's why we charged it as a second-degree felony."
Sloop on Friday waived his right to a preliminary hearing in the assault case, and Allphin set an arraignment date for Jan. 14. He was already scheduled to be in court that day for a pretrial conference in the murder case, which is set to go to trial in March.
Mauro said Friday that there are still many issues to work out before trial, including the possibility that Sloop may accept a plea deal.
"We are in the process of always talking about plea resolution," he said outside of court Friday. "We do not have a resolution, we are talking about resolution."
Davis County prosecutors have filed their intent to seek the death penalty against Sloop, citing "Shelby's Law," a 2007 amendment to Utah's homicide statute that allows prosecutors to seek the death penalty without having to prove a killing was intentional when a child dies during an act of abuse, sexual assault or kidnapping.
But Mauro has argued Shelby's Law is unconstitutional.
"He shouldn't get the death penalty because he didn't commit an intentional killing," Mauro told reporters after an August hearing.
Sloop's wife and Ethan's mother, Stephanie Sloop, 30, faces essentially the same charges in her son's death. A status hearing in her case is set for Jan. 28.
Charging documents allege Sloop and his wife severely abused Ethan between April 29 and May 8 in 2010. The alleged abuse included "beatings, burning, drugging, isolating, malnourishing, leaving the child alone and unattended while suffering, and refusing to seek vital life-sustaining medical attention," according to court documents.
The couple allegedly left the injured boy by himself in a locked bedroom while they got married on May 6, 2010. After that, Ethan allegedly suffered second- and third-degree burns after being scalded with hot water, but the couple did not seek medical attention. The boy died sometime on Mother's Day, May 9, 2010.
After Ethan's death, the couple allegedly buried the boy's body in a shallow grave near Powder Mountain Ski Resort and reported him missing. On May 11, 2010, Sloop led police to Ethan's maimed body. Sloop allegedly told investigators that he tried to disfigure the boy's face and teeth so he would be harder to identify.