The aftermath was captured on film by vegan Jessica Carter, who said she was walking nearby when she noticed the commotion in Bacchus Marsh at 2pm on Tuesday.

Ms Carter said injured and dead birds were being crammed into cages while passersby joked that those who survived would likely end up in KFC anyway.

"People were joking about it, saying KFC won't have to pluck their chickens at least now," she said. 

"It highlights to me that people are so indifferent to their suffering even after they've been through a trauma like that.

"Nobody was really showing any respect for life."

In the video, a crowd of people are seen to flip an upturned cage filled with pellets of live birds, while others gather up stunned chickens, many with bald patches that have come free onto the street.

"There were dead chickens, there were injured chickens, I'm not saying this as a vegan, it was really quite distressing," Ms Carter said.

A police spokeswoman said the crates were believed to have come off a truck as it came around a corner.

Ms Carter described the location of the incident as "poignant," and said she'd initially thought it might have been a stunt.

"The fact that there were dead and injured chickens and the way they were handling them, there's just no way that any animal group would do that," she said.

"It truly was just one of those terrible coincidences."

KFC could not be reached for comment on Tuesday night.