Prosecutors can now amend the charges to reflect the class A misdemeanor charge of negligent homicide, which carries a possible penalty of up to a year in jail.
At Wednesday's hearing, Jonathan Hummell, an eyewitness to the shooting, said Eric Charlton had consumed two glasses of Captain Morgan rum mixed with cola, and the younger boys had also been drinking that night at Yuba Lake.
The group had been telling ghost stories and became spooked when they heard coyotes in the distance. Eric Charlton, a former Marine, grabbed his .45 caliber handgun.
Hummell testified that Charlton told his younger brother, "You know you're my brother when you can trust me with this," while swinging his arm across his body. The gun fired, and a bullet passed through Cameron's left temple.
Charlton had told law enforcement that he initially removed the magazine from the gun, and even pulled the slide back to show the teens that the weapon was empty earlier in the evening, court documents state. He showed the two teens different firearm techniques before replacing the magazine. He told police, however, that he did not remember charging the gun's chamber with a live round.
Susanne Gustin, Charlton's attorney, argued in court Wednesday that is possible that if the magazine was slammed into the gun with too much force, it could load a bullet into the chamber without the operator's knowledge.
Justin Bechaver, with the state's crime lab, testified on Wednesday that about 30 percent of the time he forcefully loaded a magazine on Charlton's 1911 Springfield, a bullet was pushed into the chamber.
Charlton also faces misdemeanor charges of reckless endangerment and carrying a weapon under the influence of alcohol.