A direct reply from Elon Musk on twitter about why radar did not recognize the white side of a trailer across the road when the camera missed it: "Radar tunes out what looks like an overhead road sign to avoid false braking events" https://twitter.com/elonmusk/status/748620607105839104 EDIT: When the "overhead sign" comes down below overhead clearance of the vehicle the signal should not be masked. There should have…
A reply to that tweet: "our new Prius applied the brakes while driving under an overpass. I'm glad no one was following too close"
More likely someone confusing the brake warning with the auto-braking shutdown warning. Because it uses optical cameras, driving into bright sunlight or into deep shadows can cause the system to shut down momentarily, and it beeps to let you know.
Even best case scenario that tweet has nothing to do with this incident because the technology and systems are different. Worst case it never applied the brakes at all, and the driver got confused.