All deaths in Gaza is the result of Hamas intentionally inviting Israel in to Gaza by way of massacring Israelis and rounding up hundreds of hostages of all ages. Hamas had to know that Israel would have to respond in a very aggressive manner.
The one deal that has been on the table for 15 months is for Hamas to lay down their arms and release the hostages. That would have prevented 15 months of pure grief for the good people of Gaza.