Eventually they wound up getting evicted and abandoning all of their stuff in the middle of the night.While from a landlord prospective you may not feel the need to interject, I would strongly suggest having a good conversation with your tenant for the sake of the sanity of the neighbor. 

The Marshal deems all remaining contents abandoned.

And if they were out by midnight, I'd give them $300 cash.I made it clear the cash would be exchanged at a public location and they had to sign paperwork stating everything they left in the unit was considered abandoned.

Enough people suffered and DIED due to this brilliant idea that it was quickly abandoned.   

I told this IDIOT I had just gotten off the phone with the Police and they were literally waiting around the corner, to let me know when you show up and that I would have him arrested for mail theft since they abandoned the property under WA law in writing....Then he claimed that I told them I promised them all of their money back.

When they did not pay rent on May 1st and appeared to have moved out, did you follow abandonment procedures, or did you just enter and start the clean out?

What are the abandonment laws in your state? 

They will provide you with forms to apply for an abandoned Title.

I have several apartments near North Carolina State and University of NC - Chapel Hill and my property manager just told all her clients to expect students abandoning units in the coming weeks. 

Read your lease about abandoning the apartment.