A 46-year-old man who died at the Chester Zoo car park was carrying out maintenance work on a bus.
An eyewitness reported a 'massive bang' as the double decker came down on top of the victim on Wednesday (June 14).
The man, from Wigan, passed away after getting trapped under the coach at about 12.30pm.
He was working beneath it near the right rear wheel.
The witness said the bus came off blocks which were being used to prop it up.
He said: “I was walking into the zoo with my family. The driver was doing some work fixing the coach.
“Then there was a massive bang and it came down.
“There were other drivers stood around in the car park but no one was expecting it.”
Cheshire Constabulary released a statement saying the bus was believed to have been empty at the time of the incident.
After everyone close by realised what had happened, they started searching for a jack to lift the coach.
The eyewitness added: “I didn’t want to look underneath the bus.
“I called the police and another man said he was on the phone to them too.”
North West Ambulance Service were also alerted, but the man was pronounced dead at the scene.
Chester Zoo chief executive officer Mark Pilgrim said their 'thoughts and sympathies are very much with his family and all involved'.
The attraction stayed open but a section of the coach parking area was closed off to the public.
Police confirmed an investigation had been launched into the incident. The Health and Safety Executive have also been informed.