Moaning cockroaches

This morning, I went downstairs and opened the back door to go out on the deck before it gets too hot. A HUGE cockroach was apparently basking whatever cool air was leaking out of the door. As soon as I opened the door and the rush of cold air came over him, he made a dash for the relief of air conditioning.
Thinking quickly, I grabbed the first thing in reach with which to smash him; Zachary's Bobo toy.

Forgetting that Bobo has a noisemaker inside him, I mightily struck the cockroach, only to hear:

MWAWAAAAAAAA

My first thought was that the sound came from the last breaths of the invading cockroach. Let me tell ya, that will give you pause.