%u201CO you who believe! If a wicked person comes to you with any news ascertain the truth lest you harm people unwittingly and afterwards become full of repentance for what you have done.%u201D (Al-Qur'an 49:6)
With regards to the last part of your question, Islam forbids killing of innocent people. The Qur'an says:
%u201C %u2026 If anyone slew a person unless it be for murder or for spreading mischief in the land it would be as if he slew the whole humanity: and if anyone saved a life it would be as if he saved the life of the whole humanity.%u201D (Al-Qur'an 5:32)
Killing any innocent human being, whether Muslim or non-Muslim is not allowed in Islam. Even in the circumstances of war, this aspect is not to be ignored. The first caliph of Islam, Abu Bakr As-Siddique (R) is reported to have commanded Usama ibne Zaid (R):
%u201CI command you to do ten things: you must not kill a woman or a child, or an elderly person; do not cut down trees, or vandalize homes, or wound a sheep or camel except if you must eat it; do not drown a palm tree, or burn it, do not be treacherous; do not be cowardly; and you will pass by people who have devoted themselves to monastery life: leave them alone with their devotions.%u201D (Tarikh At-Tabari, V.3, p.210)
Thus killing children or innocent people are not allowed in Islam. And Allah knows the best.
