There is a civil war raging for the last couple of years with rebels pressuring his army severely. Yeah it's not like he would have anything at all to gain from instilling some fear in the population... And the "excuse" that they are using human shields is getting old. it doesn't work for Israel and it doesn't work for Assad.
10 arrested at Israeli Arab protest in Ramle (Haaretz)
from the article: Israel confirms Syria regime used chemical weapons against rebels