Why?

Et tu, Brute?

The knife was held in the right hand
I was unaware.
It was brought up high to brand
All that I heard was the movement of the air.

I stumbled a bit
It did not hurt.
My vision was getting less and less lit
And I looked down at my shirt.

By now it was soaked
This was all unprovoked.
And I looked up and said “Let me ask before I die”
Why?