Meanwhile, the search resumed for his still-missing mother as reports surfaced that she previously had been investigated for abusing and neglecting the youngster.
Thurston County sheriff's spokesman Chris Mealy said Friday that deputies in a boat were looking for Shantina "Kat" Smiley, 29, of Silverdale.
Smiley and her 8-year-old son, Azriel Carver, were last seen Saturday night, and her minivan was found partially submerged in a cove off Budd Inlet near North Olympia at about 11:15 p.m. Saturday.
Azriel's body was discovered Thursday by a local resident on a Fox Island beach - about 18 miles away - and Mealy said strong tidal action in the area easily could have carried the boy's body that far.
Meanwhile, Child Protective Services confirmed that it had received 10 complaints involving Smiley and her son over the past five years, and that three of the complaints had been investigated.
That portrait of the relationship between mother and son differed dramatically from an earlier statement by Smiley's fiance, Robb Simmons, that he didn't believe she would do anything to endanger her son.
According to CPS spokeswoman Sherry Hill:
• A report was filed in June 2005 that Carver suffered "serious physical abuse," including a broken arm and bruises, by Smiley's former boyfriend. The complaint was investigated, and the boyfriend was arrested for assault - but never prosecuted.
• In March 2007, CPS investigated a complaint that Smiley had physically abused her son, but the complaint was closed as "unfounded."
• Another referral was made to CPS in April 2009 about Carver "acting out" in school, but no details were immediately available. "We're still waiting to find out how much contact we had at this time," Hill said.
CPS will now conduct an extensive "fatality review," which involves going over every aspect of the case to see if mistakes were made by any agency along the way.
"We will look at all activity we had with the family ... in the fatality review," Hill said. "We're going to scrutinize every action."
Hill said it is not fair to blame CPS for the boy's death without further information.
"I dont believe it is fair to jump to that conclusion, when you have to look at people going through treatment and making an effort," she said.
"Any death of a child is tragic, and a child's death is even more troubling when that child has been served by the child welfare system and when a death is due to child abuse or neglect at the hands of an adult that was entrusted to care for them - it's even more heartbreaking. ... We continue to learn from these tragedies."
Searchers in the vicinity of Fox Island so far have found no sign of Smiley. The search is being coordinated by the Pierce County Sheriff's Office.
Deputies were able to recover several items that washed up on the beach in Budd Inlet on Tuesday night that belonged to Smiley, including leather shoes, an inhaler and an orange ball. A half-full and corked wine bottle also was found.
The missing boy's father, Jay Carver of Buffalo, N.Y., flew out to Washington state to aid in the search for his son. He said his heart sank when he heard the news that the boy's body had been tentatively identified.
"I was just hoping to find them safe somewhere to where I can come through and have them, and find them alive ... didn't play out that way," he said. "He could've offered a lot to this world. It's just a shame that he's not here."
Smiley and her son were headed from Silverdale to her stepfather's home in Castle Rock when they disappeared over the weekend.
Detectives have determined that Smiley turned off Interstate 5 in the Olympia area while enroute to Castle Rock, and was seen by several people who described her as appearing to be confused and lost.
A wallet containing Smiley driver's license, some cash and credit cards were found in the minivan, but neither Smiley nor her son was anywhere in sight.
"Apparently she got stuck and abandoned the car," Mealy said. There was no indication that a crime took place inside the 2005 Dodge Caravan, he added.
An employee at an east Olympia diner where she bought a corn dog told investigators that Shantina left without her purchase and then tripped and fell walking back to her van, but Mealy said the fall was not serious.
The elderly couple who lived nearby said they let Smiley use their phone to call her grandfather, gave her son a piece of pizza, and then directed her back to the freeway. She wasn't heard from again.
Mealy said that as she left the home, Smiley made another series of driving errors that eventually led her to a hard-to-find dirt path and driving onto the beach.
Smiley's fiance, Robb Simmons, said the woman had a drinking problem and relapsed last week.