Investigators said Saunders tried to get a handyman to let him into the apartment, but the handyman refused because Saunders didn't live there. So Saunders told the handyman he was going to kick open the door to the apartment. Saunders then handed the handyman a note that included his mother's phone number and instructions to call his mother if anything went bad, police said.
Mitchell reportedly heard someone screaming outside the door and then sounds of someone kicking the door, investigators said.
About 3:15 p.m., Saunders kicked open the door, lowered his shoulder and rushed inside the apartment at Mitchell, prosecutors said.
Mitchell fired several rounds from his handgun, killing Saunders, police said.
Prosecutors said Mitchell didn't know Saunders or his relationship to the woman he was visiting. In addition, prosecutors noted that Mitchell was legally inside the apartment whereas Saunders was not.
Prosecutors said Mitchell was an invited guest. Prosecutors noted that Saunders would visit his ex-wife at the apartment but did not have a key or live there.
Utah law allows deadly force to protect people and property particularly if the entrance is made in a "violent and tumultuous manner," prosecutors wrote.
Mitchell believed deadly force was necessary to protect himself from Saunders and was justified in using it, prosecutors determined.
"The statute presumes the person acted reasonably and had a fear of imminent death or serious bodily injury if the entry was made in a violent and tumultuous manner," prosecutors wrote. "Under these circumstances ... the use of force is justified and cannot be the basis for a criminal charge."