The sheriff's office says 5-year-old Raphael Duran Alonso of Nampa died as a result of the injuries he received in the crash Monday.
The sheriff says Michelle Lopez, 21, and Nathaniel Ortiz, 5, were also killed in the crash. They both lived in Nampa.
Authorities say the driver, 25-year-old Juan Ortiz, is at a Boise hospital with serious injuries.
Police say Ortiz and Lopez were dating and had just spent the weekend in McCall. Nathanial Ortiz is Juan Ortiz's son.
Detectives are looking to talk to anyone who may have witnessed the crash and have not already talked to law enforcement. If that's you, call 208-382-5160.