Civilian deaths were never Isreal's purpouse. Israel was responding to massive salvoes of rockets fired from Gaza in 2 days. (about 150 to be more precise) it's hard to tell what causes an explosion, be it a missile or an rpg. They both fly too fast to be seen by naked eye. it's regretable that lack of communication caused the deaths of those civilians. However, when a country is in war, it's not like a simple conversation 1 on 1 on the phone. A lot of information has to be processed fast.
Report: IDF find M-16 rifle hidden in Palestinian's car in West Bank (Haaretz)
from the article: IDF soldier claims wrong information led to Gaza family's deaths