Officers found Belton with serious head injuries and he died in the hospital Thursday.
Straub said it appeared that Belton fought back against his attackers, which may have increased the severity of his beating.
"Our information indicates the individual fought back and that may have made this a worse situation," Straub said.
Nevertheless, "I encourage people to fight back" when attacked, Straub said.
Police received a tip early Monday about Adams-Kinard's location, Straub said. Three other juveniles in the house with the suspect Monday were arrested for investigation of rendering criminal assistance, a felony.
Investigators believe the boys targeted Belton randomly. "There is no gang activity associated with this incident," Straub said.
Both suspects have criminal records for assault, he said.
Straub said the case involved twin tragedies.
"It bothers me that a distinguished World War II veteran lost his life," Straub said. But the lives of the young suspects are also likely ruined, he said.
Belton was born and raised in Spokane. He survived being shot in the leg in 1945 at Okinawa, one of the fiercest battles of the war, and went on to spend 33 years working for Kaiser Aluminum before retiring in 1982.
Belton was called Shorty by his friends because he was little more than 5 feet tall, his niece Pam Hansen said.
She believes he was targeted because of his age and size.