It sucks ass to have this happen, but you need to be honest:

Do you genuinely have reason to believe your ex would harm or endanger your child?

If the answer is "no", you have to breathe and wait until start of business. Collect all the evidence and record everything.

If the answer is yes, you DO have legitimate reason to believe your child is in danger, get together any and all evidence that your ex is a legitimate threat. Take that to the police then take it to the tribal authority if the police won't help.

It's possible your child will just be placed in the care of another relative or tribal foster family, but you'll at least know your child is safe.