Utah also has negligent homicide (essentially 3rd degree murder in other states). In mose states 2nd degree murder is manslaughter.
Utah has manslaughter.
So yes, Utah does have lesser charges if in fact she killed herself and he panicked. He would not then be reasonably charged with first degree or aggravated murder.
Manslaughter and negligent homicide still exist in Utah.
https://le.utah.gov/xcode/Title76/Chapter5/76-5-P2.html
MOO the coverup, lying to police and desecration don't indicate panic rather deliberate obstruction.
AA may have traded the body for a lesser charge.