He then walked out of the store after them, firing nine rounds at them, investigators said. Francis was struck in the back, hand and chest, and Riley in the back and leg; both later died of their injuries in hospital.
A third teen who was with the friends managed to escape unharmed.
"There was no altercation. There was, there was nothing that would have set off Battle to be angry at these kids," Deenihan said, per KMOV4.
"They literally just asked him how tall he was. 'Cause he is extremely tall. I know it doesn't make any sense."
Police released surveillance footage surrounding the shooting, which occurred over Father's Day weekend.
It showed the suspect fleeing the store, gun in hand, authorities said.
After posting the information on social media, detectives eventually managed to track Battle down and arrest him on Wednesday; he had allegedly cut off his hair in an attempt to change his appearance. He is being held without bond.
Exercising his right to silence, Battle did not give a motive for the attack, the question about his height appearing to be his only interaction with the victims.
Deenihan lamented the boys, who he described as "very good kids from really excellent families", would now never know how tall they would have been.
"The victims commented because, since Battle is quite tall, and they asked him how tall he was, and you know, hoped to be that tall someday," he said. "And unfortunately, obviously, we'll never see the full growth of these poor children."