Walker was last seen by his family March 14 and was reported missing March 19. His remains were spotted March 28 in a wooded lot off Sandy Forest Road near Munson.
Forensic evidence and witness testimony indicated Walker's death occurred the morning after he first disappeared March 15, Santa Rosa County Sheriff Bob Johnson has previously said.
Earlier this month, authorities announced that arrests warrants had been issued for both McCullers and Isaac Cameron Daniels, 19, in connection to Walker's death.
Daniels has not been arrested and remained at-large Tuesday.
McCullers' arrest report, which was highly redacted before it was released to the public, stated there was evidence to indicate Walker was killed in the same location where his body was found.