There is a wide range of difference of opinion on this, Wa ma katiluhu wa ma salibhu. They did not kill him, They did not crucify him. Another worse and he raised him up to himself. That could mean he just like when we say, woh Allah ke pass chala gaya or woh Allah ko payara ho gaya.
Unno ne Isa ko nahi mara, lekin Allah ne unko utha liya. Zururi nahi hai ke zinda haalat mein, shaheed ki misaal bhi di jaa sakthi hai. Is duniya se to woh chale gaye lekin maray nahi.
Think logically if such a HUGE event is supposed to take, don't you think Quran would have mentioned it, yet it is totally silent about it. All books told about the coming prophets hence one of the first person to recognize and realize that Muhammad s.a.w when he was still young and had not yet received prophet hood would be a prophet was a jewish monk, because of what he had read in his scriptures about a coming prophet.
So the Quran should have mentioned such a glorious event in at least one verse? Yet there is nothing.