This is the heart-stopping moment a train driver makes an emergency stop to save a petrified dog chained to a railway. The driver has been hailed a hero after halting the massive locomotive, climbing down from his cab and freeing the defenceless animal.

Authorities say they are ‘shocked’ at the cruelty of those responsible and have launched a full investigation.

WATCH: Train stops feet away from dog chained to tracksA video taken by the train driver shows him saying: ‘How can there be people so bad? Who leave little dogs tied up on the tracks. You cannot do that. I hope someday the human race changes.’

The panicking dog can be heard barking and growling as it tries to escape. Local media say the dog ran from the scene as soon as the driver freed it. Authorities in Llay-Llay, Chile, say a criminal investigation has been launched into the video which has fetched over 137,000 views online.

Source: Metro