Photo: Florida Highway Patrol investigators

Joshua Brown, the Tesla driver killed last year while using the semi-autonomous Autopilot mode on his Model S, received several visual and audio warnings to take control of the vehicle before he was killed, according to a report from the National Transportation Safety Board. Despite the warnings, Brown kept his hands off the wheel before colliding with a truck on a Florida highway.

The new details of the crash were revealed in more than 500 pages of records collected as part of the National Transportation Safety Board’s ongoing investigation into the 2016 incident.

The May 7, 2016 crash drew widespread attention for being the first known fatal accident involving a vehicle operating on its own. The advent of autonomous cars makes for a fascinating moment in history, as new technology always draws interest from a wide swath of society. As you might expect, there was an inordinate amount of coverage on the crash. You might recall, Brown was driving along a Florida highway in his 2015 Model S70D, when he collided with a tractor-trailer. Data from the vehicle’s system revealed Brown was operating the car using automated control systems like traffic-aware cruise control and Autosteer.

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And as Reuters notes, Brown kept his hands on the wheel for only 25 seconds of an extended 37-minute period, in which the NTSB said he should’ve maintained control of the vehicle. Here’s more

The report said the Autopilot mode remained on during most of his trip and that it gave him to a visual warning seven separate times that said “Hands Required Not Detected.”

In six cases, the system then sounded a chime before it returned to “Hands Required Detected” for one to three second periods.

Though the NHTSA didn’t find any evidence of a defect with Autopilot, the regulator’s report later stressed the need for drivers to still pay attention while using Tesla’s Autopilot. The NTSB’s report reiterated earlier findings that Brown wasn’t watching a DVD, contrary to initial witness testimony.

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In a news release, the National Transportation Safety Board said that no conclusions about the crash should be drawn from the docket, and any findings, recommendations and probable cause determinations related to the crash will be issued by the board at a later, undetermined date. But the docket makes for an insightful read into one of the biggest stories in the auto industry over the last two years.

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The board’s investigation is separate from the National Highway Traffic Safety Administration’s probe, which earlier this year cleared Autopilot in the accident and didn’t order a recall. The accident docket—which you can view here–includes a crash reconstruction report, witness interviews, toxicology reports, and more.