It is possible that the russian mafia murdered the family. Perhaps they refused to pay protection money and murder was the mafia's response. The family was at their restaurant business until 4:30 in the morning. They must have got some warnings and they may have been afraid that the premises will be burned down or something other will happen to it.
Syrian rebels call for regional alliance against Russia and Iran (Reuters)
from the article: Police to probe Russian Mafia ties to Rishon family murder