Beep, then "stop safely now" appears in mileage window, then black. on 2008 Ford Escape Hybrid

This happened on the freeway after driving about 20 minutes outside it was dry and about 60 degrees F. After I safely coasted to the shoulder and cried a little, it started back up with no indication it had gone dead. Is this a sign of something bad?

Asked by for the 2008 Ford Escape Hybrid