Background: News footage of the property in Aberdeen, Wash., where Aiden Bevins was found on May 15 (KING). Inset: Aiden Bevins (Facebook).

The father of a 4-year-old Washington state boy found buried in his grandmother's backyard has been arrested on suspicion of murder.

According to local NBC affiliate KING, the Aberdeen Police Department arrested 36-year-old Jacob Scott Bevins, the father of 4-year-old Aiden Bevins, whose body was found buried on a property in Aberdeen, Washington, on May 15. KING reported that police became aware that Aiden was missing after receiving a previous complaint about the whereabouts of Bevins' 6-year-old daughter on May 12. The little girl was with her mother.

Relatives then told police that they had not seen Bevins' son for a long time.

KING spoke to Aiden's family members, who said they asked police for a welfare check at the home of the boy's grandmother, where he was said to be living with Bevins. Police told them that they questioned Bevins when they were at the property in connection with the search for his daughter. He allegedly told police that Aiden was staying with relatives in another state.

According to KING, police contacted those relatives, and they said the boy was not with them, and they had not seen Aiden at all. Police returned to Bevins' home on May 15, this time with the Washington State Patrol Crime Scene Response Team. Detectives interviewed Bevins again, conversations that police said led to the discovery of Aiden's body buried in the backyard.

A cause or manner of death has not been released yet.

Aberdeen police arrested Bevins on Friday on suspicion of second-degree murder, first-degree manslaughter, unlawful disposal of human remains, and making a false or misleading statement to a public servant. He is currently in custody at the Grays Harbor County Jail, where he is being held without bail. He has not been formally charged yet.

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KING reported that Aiden had been under the care of foster parents, Gary and Magali Lopez, for several years. Magali Lopez told the station that she had contacted authorities, including Child Protective Services and the Department of Children, Youth, and Families, in regard to Aiden's biological parents. Despite the repeated concerns, Magali Lopez said Aiden was still returned to his biological parents.

She told KING, "I can't explain to you the anger that I feel. Everyone failed him."