World-renowned brain surgeon Derek Shepherd has died.

The talented doctor, whose car was broadsided after he helped to rescue victims of another accident, died Thursday shortly after doctors failed to properly diagnose the extent of his injuries.

A preeminent neurosurgeon, Shepherd's career hit a zenith just last year when President Barack Obama personally offered him the opportunity to lead a brain-mapping initiative for the National Institutes of Health.

"It's a beautiful day to save lives," Shepherd was known to say. "Let's have some fun."

The only son of a New York-based navy nurse and a convenience store owner, Shepherd and...