This song is very sad, do you know why?

A normal day,
everything seems all right
A thirteen year old,
with a gun in his hand
He left for school,
waving goodbye
Not knowing that now,
there is no way back.
All that was given,
he will take it away
He doesn't even care,
there are more to blame.
Then shoots a poor girl,
that was running late
She falls and she bleeds,
with no time,
with no time to flee.

You don't understand,
you don't understand
When you take a life,
you are taking mine
You don't understand,
you don't understand
What we've been growing with patience and love
has fallen apart

The feeling of pain,
never felt it before
I know it's not easy,
that there isn't a cure.
Stop looking away,
Quit turning around
Silence and violence would sure turn you down.

You don't understand,
you don't understand
When you take a life,
you are taking mine
You don't understand,
you don't understand
What we've been growing with patience and love
has fallen apart

A normal day,
everything seems all right
A thirteen year old,
betrayed by his dad

He left for school,
waving goodbye
Not knowing that now,
there is no way back.
I'm filling my time with messages of hope
I'm filling my time with thoughts of love

You don't understand,
you don't understand
When you take a life,
you are taking mine
You don't understand,
you don't understand
What we've been growing with patience and love

You don't understand,
you don't understand
When you take a life,
you are taking mine
You don't understand,
you don't understand
What we've been growing with patience and love
has fallen apart.