Amazon has some explaining to do.

The online retail giant has been caught providing facial recognition technology to law enforcement in Oregon and Orlando, according to documents obtained by the American Civil Liberties Union through a Freedom of Information Act Request.

Emails obtained through the request show how Amazon has been advertising and selling its facial recognition product, Rekognition, for only a few dollars a month to law enforcement agencies — in the hopes that they would encourage other agencies to sign up. The emails also show Amazon has marketed consulting services to law enforcement as well.

In addition to disclosing the emails, the ACLU led a group of more than two dozen civil rights organizations to pen an open letter to Amazon on Tuesday, calling on the company to stop selling facial recognition software to law enforcement because it promotes the use of mass surveillance in a way that could disproportionately affect vulnerable communities.

"Amazon Rekognition is primed for abuse in the hands of governments," the letter reads. "This product poses a grave threat to communities, including people of color and immigrants, and to the trust and respect Amazon has worked to build."

Mashable contacted Amazon for comment, and we'll update this story when we hear back.

According to Amazon's own marketing materials, Rekognition is capable of identifying "thousands of objects and scenes" in live video. The examples Amazon uses is that it can identify specific activities such as "person delivering a package" or "person playing soccer." In law enforcement, the software is able to track 100 faces at a time — even if some of those faces may not be visible for every second. A similar technology is used to power Amazon's new cashier-less convenience stores, Amazon Go.

What is perhaps most terrifying about this new revelation is that Amazon isn't the only powerful tech company building and marketing such services. To cite one example, Microsoft also sells a facial recognition service to law enforcement called Face API. While some instances of this technology make sense — say at concerts or malls — it takes on an entirely different meaning when it's used to surveil innocent people in public places, especially with no or little oversight or clear guidelines on when such an act may or may not be appropriate.

So where do we go from here? Well, Amazon will likely continue to sell its facial recognition software in addition to many of its greatest competitors. It's hard to imagine this playing out any other way when even companies like Ticketmaster are finding novel ways to use this technology.