An anonymous Amazon staffer has posted a letter in which he claims that 450 fellow staffers wrote to Jeff Bezos, protesting the company’s decision to sell its Rekognition facial recognition software to US law enforcement agencies.

This technology, Amazon claims, uses a machine-learning pattern-matching tool for video and photographs that enables “real-time face recognition across tens of millions of faces” and detection of up to 100 faces in crowded photos.

“Our concern isn’t about some future harm caused by some other company: Amazon is designing, marketing, and selling a system for dangerous mass surveillance right now,” the unnamed employee writes.

“Amazon’s Web site brags of the system’s ability to store and search tens of millions of faces at a time. Law enforcement has already started using facial recognition with virtually no public oversight or debate or restrictions on use from Amazon.”