Hello T.,
I presume you cannot contact the original owner because the owner is deceased. You only option that I can see would be if you could contact the inheritor of the deceased's estate. That person would have to apply to Apple for control over the person's account and could then remove the lock using the log-in information. Here are some articles you may find useful should you decide to go through with this:
How to remove Activation Lock - Apple Support
How to request access to a deceased family member's Apple account - Apple Support
Apple can remove a lock if a person can provide sufficient evidence of valid ownership. Do this online here --> https://al-support.apple.com/#/additional-support Apple says, "Proof of ownership documentation is required," but does not state what constitutes proof. This might be similar to what is required in the previous section.