Muchas gracias por la respuesta, Angelica.
1. Sounds sensible. So essentially,
no se tiran personas; se tiran balas. And
una persona le tira a otra persona. Grammatically speaking, it's almost like "to shoot someone a text" rather than "to shoot someone or somebody".
2. That explains a lot.
3. Okay. So the choice of mood emphasizes, regarding the deaths, their mortality rather than their activities.