Sounds like the auto-flight had "captured" 5,000' during which time the crew reselected 11,000'. On the 75/767, during this phase of flight, "alpha" protection is removed. The A/P would have tried to pitch up to obtain 11,000 with the sudden reduction in airspeed. Not a good system.
A similar situation happened to me over the Rockies about 20 years ago. We were just acquiring FL390 when we encountered a strong decreasing-performance wind shear. The aircraft was in "acquire" mode when the nose pitched up to try to maintain FL390. I watched the airspeed roll back 30 knots almost instantly.