After all of the apologies and after all of the regrets expressed by Israeli Prime Ministers past and present, Yediot Aharonot, inter alia, reports:

An IDF investigation has found that the building in Qana struck by the Air Force fell around eight hours after being hit by the IDF.
[…] Eshel and the head of the IDF’s Operational Branch, Major General Gadi Eisnkot said the structure was not being attacked when it collapsed, at around 8:00 in the morning.
The IDF believes that Hizbullah explosives in the building were behind the explosion that caused the collapse.

Another possible explanation is that the IDF-compromised building fell hours later as a result of volatile materials which were left in the building. So, perhaps Amir Paster didn’t have to desert the IDF in protest of the civilian killings?