How does Walter White die in Breaking bad
In the final episode of Breaking Bad, Walter attempts to clean-up his mess by killing off all those who betrayed him, and rescue Jesse from his captors.  Walter builds a moving arm mount for an M60 machine gun that he can activate from the car's remote key fob, and places it in the trunk of a car that he got from the same gun dealer.  Walter then drives to the compound where the Aryan Brotherhood are living, under a trick that he can help them make “meth” with a new recipe.

Once inside, Walter Argues with Jack about why Jessie isn’t dead yet, causing the angry Jack to bring Jessie into the room to prove they are not friends.  AT this point, Walter charges Jessie to the floor and presses the key fob, causing the M60 to begin shooting into the building.

Everyone in the building is shot dead except for Jessie, Walter, Todd and Jack.  Jesse strangles Todd to death with his handcuffs, and Walter Shoots Jack with his own gun.  Jessie then leaves the compound in one of the cars that is sitting outside.

After this, you become aware that Walter was hit by a ricochet while the M60 was firing, and has effectively been shot in the stomach.  He walks over to the building where Jessie was making Meth, and falls to the floor seconds before the Police enter the building.