this goes to hit detection

is'nt it odd that in the last seccond that you hit someone with an over powered weapon or when someone he's at low hp, the person you shot kills you first and damage doesn't affect the person you shot
besides the lag, this happens often to weapons with pistols , smg , or close range weapons
even to the sniper rifles, this happens too
another thing that i hate is that why don't people die when they get hit in the head
i know this time that i used a deagle in ship tdm. I was in the second floor and i shot someone in the head far away. how much damage did he take? 98. close to dying but still alive
(correct me if this stuff doesn't make any sense to you)