A Queensland man found dead in a car with his baby boy was pulled over by police on the same day the child's mother reported them missing.
An independent investigation is underway into how police handled the case.
Police have revealed that officers pulled the man over on Sunday, breath tested him, fined him for speeding and then let him go.
The child's mother had raised concerns about the pair with police that same day.
Their two bodies were found in a car in a remote location on the Sunshine Coast on Wednesday in a case that's being treated as a murder-suicide.
Assistant Commissioner Sharon Cowden, from the police Ethical Standards Command, says there's nothing to indicate the baby was in the man's car when he was pulled over.
But she said every aspect of the case would be investigated, including why an amber alert, used in major child abduction cases, was not issued.
"The mother contacted police on Sunday. The deceased male was intercepted by police on Sunday," she told reporters.
"We did a breath test and he was issued with a speeding ticket.
"I don't have any indications that the child was with the man at the time, but I can't understand the full circumstances this early. But the child, as far as I'm aware, was not seen at the time."