Why did Walter kill himself?

He had no control for so long in his life, with the threat of cancer taking away that final choice acting as an ultimate cruelty. By bleeding out from a gunshot wound surrounded by lab equipment, he is able to go out on his own terms. Another layer of absolution is added by Walt not even receiving the death he wants.

Who killed Walter?

On October 26, 2020, Walter Wallace Jr., a 27-year-old African-American man, was shot by Philadelphia police officers Sean Matarazzo and Thomas Munz in Cobbs Creek, Philadelphia, Pennsylvania.