Even if they were fearful, feelings alone does not entitle one to act with lethal force. There must be reasons to believe that one's life is in imminent danger. Additionally, even if the mob's violence was caused by panic, the soldiers would still not be guilty of murder since they did what they have to in order to survive the situation.
You don't need a crystal ball. Empirical evidence does not support the claim that regular encounters with Israeli enforcers will have a high probability of death.So they are to blame for lacking a crystal ball and possibly expecting the worst from people they believe to be heavy-handed aggressors. In international waters.