The National Transportation Safety Board said Tuesday that the driver of a Tesla Model X who died after his vehicle crashed on Highway 101 almost two years ago was playing a video game on his phone at the time of his accident.

NTSB Chairman Robert Sumwalt made the revelation at a hearing on the cause of the March 23, 2018 accident that involved driver Walter Huang, who later died of his injuries at a hospital.

Huang, an Apple employee, was driving from his home to Foster City to his workplace in Sunnyvale at the time of the accident. The NTSB described Huang as a game developer who frequently used gaming applications on his phone, and that cell phone records and data received from Huang’s phone showed an gaming application was in use when the crash occurred.

The NTSB said that while data couldn’t determine if Huang was holding his phone just before the accident happened, “the Tesla car log data showed that there was no driver-applying steering wheel torque, indicating the hands were likely off the steering wheel during this time period.”

One of the main issues surrounding the accident is the use of Tesla’s Autopilot technology. Autopilot gives a Tesla some partial self-driving features, such as lane recognition and the ability to keep a safe distance from other cars, but doesn’t make a Tesla a fully self-driving car.

The NTSB said that in addition to Huang likely being distracted by the game on his phone, the probable cause of the accident included the Tesla’s Autopilot system steering Huang’s Model X into a so-called “gore point”, or the area between southbound Highway 101 and the exit ramp leading to Highway 85, where the car crashed into a barrier. The investigation found that the Model X’s forward collision system failed to send an alert signal, and its automatic emergency braking system didn’t activate before the collision occurred.

Sumwalt was critical of drivers’ understanding, in general, of how technologies such as Autopilot work.

“If you own a car with partial automation, you do not own a self-driving car,” Sumwalt said. “So don’t pretend that you do.”

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Elon Musk’s wealth exceeds $100 billion; Jeff Bezos worth twice as much But, Sumwalt also had some harsh words for Tesla about its lack of response to two NTSB recommendations about vehicle automation systems. Sumwalt said the NTSB sent the recommendations to six automobile makers more than two years ago, and that Tesla was the only manufacturer to have not yet responded to the NTSB about the matter.

“We ask that recommendation recipients respond to us within 90 days. That’s all we ask,” Sumwalt said. “But it’s been 881 days since these recommendations were sent to Tesla and we’ve heard nothing. We’re still waiting.”

The NTSB also said that if Tesla doesn’t move to incorporate system safeguards that limit Autopilot’s use to the conditions that it was designed for, “continued use of the system beyond it’s design domain is foreseeable and the risk for future crashes will remain.”

Officials with Tesla didn’t immediately return a request for comment.

Earlier this month, the NTSB released documents in which Huang’s relatives said he had complained about problems with his car’s Autopilot system on multiple occasions.

Huang’s family has brought a wrongful death lawsuit against Tesla, and is also suing the California Department of Transportation for failing to properly maintain the section of Highway 101 where Huang’s accident occurred.