5:70 says that some messengers were killed. "We had already taken the covenant of the Children of Israel and had sent to them messengers. Whenever there came to them a messenger with what their souls did not desire, a party they denied, and another party they killed."
but 10:103 says God saves his messengers and the believers. "Then We will save our messengers and those who have believed. Thus, it is an obligation upon Us that We save the believers."
We know that God saved Noah, Moses, Lot and other messengers when the disbelievers were destroyed. Maybe it means the messengers are saved from destruction but they can still be killed?