What is the way they determine someone died before covering them up?

There are stories I've heard of over the years, people who's heart stopped, were brain dead, fell under ice rivers for half an hour and miraculously survived. So there are many instances of unexplained recoveries.

How do the medical teams or doctors determine then that this person won't all of sudden get a heart beat back?

See this story from the shooting a few days ago

Here's another story, and a third one.

What is the way they determine someone died before declaring them dead?

There are stories I've heard of over the years, people who's heart stopped, were brain dead, fell under ice rivers for half an hour and miraculously survived. So there are many instances of unexplained recoveries.

How do the medical teams or doctors determine then that this person won't all of sudden get a heart beat back?

After so many stories of people that supposedly died and then waking up, why don't they have some procedure where they can make sure they don't bury people alive.

I found this story from the shooting a few days ago and I've read quite a few of these kind of stories over the years. Shouldn't they wait? Or perhaps put some kind of sensor that detects any life?

Here's another story, and a third one

What is the way they determine someone died before covering them up?

There are stories I've heard of over the years, people who's heart stopped, were brain dead, fell under ice rivers for half an hour and miraculously survived. So there are many instances of unexplained recoveries.

How do the medical teams or doctors determine then that this person won't all of sudden get a heart beat back?

See this story from the shooting a few days ago

Here's another story, and a third one.