Well this is what's on Wookiepedia:
Han, Chewie, and Anakin (apparently his youngest son wtf) were evacuating people off the doomed planet.
"As the winds picked up, Anakin was knocked into the distance, causing Chewie to run after him. Chewie was able to bring Anakin to safety on the Falcon, but another blast of wind knocked him out of reach. Anakin piloted the Falcon, while his father stood on the entrance ramp hoping to lift Chewie up, but was forced to flee from Sernpidal when he realized it was too late to save Chewie. The Wookiee stood in the moon's trajectory, howling defiantly, and was crushed to death with those Sernpidalians who could not escape. His death drove Han to a resentment of his son Anakin. Han eventually recovered and forgave his son, but the death of his battle-brother and dearest companion would stick with him forever."
Not quite as stupid as Chewbacca thinking he can just palm a moon to stop it, but still...meh.