The first death (In the garden of Eden is about to occur).  God is going to sacrifice an animal to cover their sin.  Off with the aprons, on with the animal pelts.  God made them coats.  I wonder if this implies that they were going to have to suffer " the cold".   They will be cursed with horrible weather I am sure.

Gen. 3:21  "Unto Adam also and to his wife did the Lord God make coats of skins, and clothed them."
This is the beginning of sacrifices among the people of God.  It makes the phrase, "The lion will lie down with the lamb,"  all the more meaningful.   That's the description of heaven:  Nothing, or no one, will  need to  be afraid of being killed ever again.

Death has come.  But that's not the worst of it.

Gen. 3:22-24a "And the Lord God said, Behold, the man is become as one of us, to know good and evil: and now, lest he put forth his hand, and take also of the tree of life, and eat, and live forever: Therefore the Lord God sent him forth from the garden of Eden, to till the ground from whence he was taken.  So he drove out the man,,,"

There is a phrase in that section: "...lest he put forth his hand, an take also of the tree of life, and eat, and live forever..."   Adam was now denied the Tree of Life.   His future, which could have stretched out in front of him forever, was now doomed.  He was denied Life.  He was now one of the living dead.  God told him if he ate of the fruit of the forbidden tree he would die.  He died.

So Adam is now dead.  He just doesn't know it yet.  Without Life, all humans are dead.  You have to have Life to be alive!!  Romans l6:23 "For the wages of sin is death; but the gift of God is eternal life through Jesus Christ our Lord. "

The ultimate sacrifice is far in the future.  But this explains why Christ is called the "Tree of Life."