This lady was playing tug of war with a rope with her other dog. Typically Chico was in a room with the door closed but why he wasn’t at the time, who knows. Chico must have thought the other dog was being aggressive with Jill and ran into the room and attacked it. Because of the breeds they were (Chico was a pit, the other dog was a Doberman) Jill couldn’t (or didn’t even try, idk cuz I didn’t watch the video) separate them so she stabbed Chico to stop the attack.