Mike Ey, a key project designer on Microsoft's HoloLens headset, has been killed in a hit-and-run in Redmond, Washington.

Ey was killed when his vehicle was rear-ended by another going over 100 miles per hour (160 kmph), said state police.

The driver of the second vehicle, who had allegedly been drinking, fled the scene but was tracked down by a police canine unit. The driver now faces vehicular homicide and felony hit and run charges.

"He was the most reliable person ever," said Ey's girlfriend, Kelley Piering. "You could ask him anything and he would make sure it got done, whether he knew how to do it or not."

Ey was working at Microsoft on HoloLens, which has been described as the first augmented reality holographic computing platform. It comes with a set of APIs that will enable developers to create holograms in the real world.

The holograms will be visible through the lens, overlaying the user's normal vision, much like augmented reality.

Piering said Ey described HoloLens as "the coolest thing ever."

"It's looking at the future while holding the present. Mike said it wasn't perfect but it was going to be one day."

Ey was 30.