Improv of "Dead Horse"

The best part of this poem was the one line of dialogue. The whole poem is one scene involving a dead horse and then the father utters one short, gut punching line. "Happens." The death of the horse just happens...what else could just "happen?"

It had to have been about four,
sun burning pavement just under the pear tree,
when the window shattered with the burnt sienna
from the brick pile outside, meant for the in progress pizza
oven made for my mother.
When my dad pulled up, back from the bank,
discovering glass shards among the wool of the welcome
mat, 
my father said: "happens."
I suppose it does-when your father,
the ex- con, returns from Rikers Island