This is fairly common at this stage of the cycle. Back in the mid 90s I had friends who got in the business of buying REO properties in the Inland Empire to fix up and quickly flip for a profit.

Unfortunately, they had to fight with squatters who had moved in when the properties were unoccupied. Calling the police was useless: the squatters usually claimed that they were tenants, some even produced fake rental contracts. At that point the cops give up and say that this is an issue for the courts.