Prosecutors in Island County have filed what is believed to be the first criminal charge for a violation of Washington's 2014 gun background check law.

KING-TV and Northwest News Network report that prosecutors say 25-year-old Mark Mercado sold a handgun to David Nunez in November 2015. Authorities believe the gun was used the next night to murder 17-year-old John Skyler Johnson. Nunez has pleaded guilty in the murder along with three co-defendants.

Washington voters approved Initiative 594 in 2014. It requires people transferring a firearm to go through a federally licensed firearms dealer to conduct a background check on the buyer. But prosecutors say Mercado sold Nunez the .22-caliber pistol without any such check.

Nunez didn't have a criminal record, but he wasn't allowed to buy a handgun because he was under 21 at the time.

Charging papers filed Friday say Mercado left his job and moved out of Oak Harbor after being questioned in the case. Authorities say they don't know where he is.