Tesla driver said he was using Autopilot when he fatally hit a motorcyclist

• A Tesla Model S driver told authorities he was using Autopilot when he fatally hit a motorcyclist last week.
• Feds this week questioned whether Tesla's December recall was enough to ensure driver attention.
• Tesla recalled over two million vehicles and installed an update to increase alerts in Autopilot.

A 56-year-old Tesla Model S driver said he was using Autopilot when he hit and killed someone on a motorcycle last week about 15 miles outside Seattle.

The Washington State Patrol's affidavit said the driver was arrested on suspicion of vehicular homicide "based on the admitted inattention to driving," while on Autopilot mode and using a cell phone while driving, according to a CNBC report. The department did not respond to Business Insider's request for records.

The driver told a Washington State Patrol trooper that he was in Autopilot mode and looked at his cellphone while the Tesla was moving, according to the CNBC report.

"The next thing he knew there was a bang and the vehicle lurched forward as it accelerated and collided with the motorcycle in front of him," the trooper wrote in a probable-cause document, according to CNBC.

On Friday, federal regulators announced they are looking into whether Tesla's recall of two million vehicles in December was enough to make sure the driver-assist technology stops driver misuse.

The National Highway Traffic Safety Administration announced it was opening an investigation to "evaluate the adequacy" of the December recall to "address misuse, mode confusion, or usage in environments the system is not designed for."

The new investigation will look into Model Y, X, S, 3, and Cybertruck vehicles with Autopilot made between 2012 and 2024, according to the NHTSA report.

In December, Tesla recalled over two million vehicles to update the Autopilot software. The recall stemmed from a two-year NHTSA investigation that identified at least 13 crashes with at least one fatality and multiple serious injuries. The software update aimed to improve driver awareness by increasing warnings and alerts.

The NHTSA document stated that Tesla said "a portion of the remedy both requires the owner to opt in and allows a driver to readily reverse it."

It's not known whether the driver involved in the Washington accident had the software update installed in his Tesla.

According to NHTSA documents, most newer Teslas have software that would automatically update.

In a document published Thursday on the recall query, the NHTSA notes that the term "Autopilot" may lead drivers to think "the automation has greater capabilities than it does and invite drivers to overly trust the automation."

Tesla's website states Autopilot mode does not make the vehicle autonomous and drivers must use additional caution and pay attention.

Tesla did not immediately respond to a request for comment.