Federal investigators found that a man who died in a Tesla crash was playing a video game at the time of the accident. And they had some harsh words for both Tesla and Apple.

The National Transportation Safety Board held a hearing Tuesday about the March 2018 crash on U.S. Highway 101 in Mountain View, California. During the hearing, Chairman Robert Sumwalt made clear that Tesla has to be better at explaining how its partially autonomous driving system works.

"You cannot buy a self-driving car," he said at the start of the hearing.

The family of Walter Huang, a 38-year-old Apple engineer, sued Tesla after his Model X crashed into a highway road barrier. The family claimed the Autopilot feature was at fault.

Records from Huang's phone logs show one of his two Apple-issued iPhones was logged in and playing Three Kingdoms, a mobile video game, at the time of the crash. The agency still found Tesla culpable in the fatal crash, but blamed the video game for the driver's "lack of response" when the vehicle started driving dangerously.

An Uber self-driving car was involved in a fatal accident in Arizona the same month as the Tesla crash. In that case, the safety driver monitoring the vehicle was watching TV on her phone in the driver's seat.

Tesla's Autopilot requires drivers to maintain contact with the steering wheel at all times and keep both eyes on the road. That includes when the car is changing lanes or accelerating.

The NTSB has chastised Tesla for years about its driving assistance system. As Sumwalt emphasized at Tuesday's hearing, the NTSB wants Tesla to make it clear to drivers that its cars can't drive themselves.

A few of the NTSB's nine new safety recommendations were directed at Apple and other smartphone makers. Sumwalt berated Apple for not having a clear personal electronic device policy for its employees.

"Apple is not a leader at all," he said. "It's lagging. It has no such policy."

Apple says its employees are expected to follow the law.

The NTSB went on to recommended Apple and others implement a "strong cellphone policy to reduce distraction," going as far as to force phones to default to a disabled mode while driving unless in an emergency.

Apple's iPhones and CarPlay system already have a "Do Not Disturb While Driving" mode available, but it doesn't go on automatically just because a user starts driving.

A recent Reviews.org survey found more than 75 percent of respondents consider themselves addicted to their phones. More than 50 percent of 500 adults surveyed said they always or sometimes look at their phone while driving. In semi-autonomous cars, it's easy to see why drivers might be easily distracted by their smartphones.