Criminal charges will not be filed against a man who was arrested on suspicion of killing his fiancee's disabled foster child, authorities said Tuesday.

Police had insufficient evidence against Louis Ross, 38, of Oakland to link him to the Aug. 10 disappearance of 5-year-old Hasanni Campbell, Alameda County Assistant District Attorney Tom Rogers said.

Ross will be released from jail and help with the search for the boy, his attorney John Burris said.

Police have said the case has changed from a missing person inquiry to a homicide investigation. No body has been found. Further details were not released.

The decision to release Ross came a day after his fiance, Jennifer Campbell, 33, was released from county jail without charges being filed.

Ross has said the boy, who is Campbell's biological nephew, disappeared after being left near the back entrance of an Oakland shoe store where Campbell works.

On Monday night, Campbell, who is six months pregnant, attended a vigil at United Presbyterian Church and said neither she nor Ross would ever harm the boy.

"All I know is it was one of the most difficult times of my entire life, and I haven't lost focus and I'm still focused on finding Hasanni," she said. "We had nothing to do with it."

The couple has cooperated fully with police in their investigation, Burris said.

"There was never sufficient evidence against either of them," he said.

A police search warrant affidavit indicated Ross sent an expletive-filled text message to Campbell 10 days before the boy went missing, threatening to leave him alone on a train station platform.

Sherri-Lyn Miller, a volunteer whose company has created T-shirts and fliers during the search, said the focus should be on locating Hasanni, not on Ross and Campbell.

"We're not going to treat him as a homicide victim like the police because we don't know that yet," Miller said. "It's time to bring this baby home."

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