The meaning of the word 'inert' is 'not moving'. In the excerpt, it is described that the machines were not moving, as if they were dead. The word 'inactive' has the same meaning - it stands for something that is not operating, moving or is out of function. This is why we could replace 'inert' with 'inactive' in this example.
The 2017 Las Vegas shooting was a mass shooting on the night of October 1, when a gunman opened fire on a crowd of concertgoers at the Route 91 Harvest music festival on the Las Vegas Strip in Nevada.
