Ernest Ruiz III, 36, of Eugene, Oregon, was arrested on a charge of unlawful possession of a firearm in connection with the murder of Kyle Anderson. That brings the arrest total to two.
Idaho County Sheriff Doug Giddings said they aren't looking to arrest anyone else at this time.
"We are at the phase where we have the folks that we want in jail, and we are now at the fact finding," said Giddings. "We want to know the absolute truth of who did what. So we come to the absolute truth of what happened."
Jason Andrew Godwin, 48, was the first suspect arrested. He faces second degree murder charges.
Investigators believe Kyle Anderson was shot while attaching license plates to his motor home.