The residents are considered suspected drug dealers or warehousers. That is the default assumption whenever police investigate an armed home invasion.
Looks like the police came up empty-handed with that assumption.
The police found nothing that incriminated the residents. The "tell" is that none of them were charged with a crime, although it appears they were arrested and then released.
They aren't going to get their weapons back.
Yes, they will, under Arizona law.