Keats, "Ode on a Grecian Urn" –

Thou shalt remain, ... a friend to man, to whom thou say'st,
"Beauty is truth, truth beauty,
– that is all Ye know on earth, and all ye need to know."

... as for "Nor easily understood"
I agree, I do not understand how police killings and suicides are correlated:

The most beautiful thing we can experience is the mysterious. It is the source of all true art and science. He to whom the emotion is a stranger, who can no longer pause to wonder and stand wrapped in awe, is as good as dead; his eyes are closed.