The video shows many cattle Dead Right There . DRT with little struggle. Electric shock could do that. Not likely that poison gas would do that without some signs of animals at the edge of a toxic cloud.
Heat doesn’t kill everyone in place. Neither does infection. In both cases, there is agonal struggle.
It is devastating for anyone who has had care and custody of these cattle.
The cattle have been placed there by the skid steer, likely to transport to burial site, or burial right there after a big hole is dug.