Updated

Two brothers wanted in the disappearance and presumed slayings of a Washington state couple have been charged with first-degree murder, and authorities believe they may be heading for the Mexican border.

Detectives found a car in Phoenix that had been driven by John Blaine Reed and his brother, Tony Clyde Reed, and they said two friends of the brothers gave them a different car — a gold Acura sedan — and $500, knowing they were on the run from police.

A license plate reader captured the Acura's plate near Calexico, California, on Monday, authorities said.

The brothers are wanted in the disappearance of John Reed's former neighbors, Patrick Shunn, 45, and his wife, Monique Patenaude, 46, who were reported missing a week ago. Investigators say they found evidence the couple were killed.