The state's attorney general's office said officers would present to suspects documents with forged letterhead and contact information and, in two cases, a signature from a made-up employee.
The mass exodus comes at a delicate time for many communities large and small as violent crime is on the rise and recruitment remains difficult.
The video of George Floyd's death was critical evidence in the murder trial of convicted ex-Minneapolis police officer Derek Chauvin. That video and others are changing trials and police training.
A review from public safety experts and world economists says the benefits to society and police departments outweigh the costs of cameras.
Some officers are being investigated over involvement at the protests, while others fought off protesters who once supported them.