He (sallallahu alaihi wasallam) wasn’t killed.
Prophets are alive in their graves but they are not alive like us.

Who Killed Muhammad sallallahu alaihi wassalam? If we believe that those who are dead are in graves, how did Muhammad lead them (the prophets who are dead)in SALAH during Isra and Miraj?

Biography of the Prophet salla Allahu alahi wa sallam | February 17, 2014 10:12 pm
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A sister is asking most people use umm Ahmad, umm Rana , such name, but Prophet Mohammed is most time been addressed in his name instead of Abu Qasim ,and khadijah his wife is not addressed as Umm Qasim in most case ,is this sunnah? and why?
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One our college is asking regarding Prophet Mohammed’s Janaza Namaz is prayed , from him information janaza namaz not prayed