An Uber driver in Denver shot and killed a passenger Friday morning, claiming he fired shots in self defense, reports the Washington Post — it is being investigated as a first-degree murder.

The backdrop: This comes amid concerns about the ride-sharing company’s ability to properly screen its drivers, as well as allegations of sexual assault and rape involving Uber drivers. The company prohibits drivers and passengers from bringing firearms into vehicles while using the app. A company spokesperson told the Post they're working with authorities during the investigation. She declined to say when last the company did a background check on the driver, Michael Hancock.