Armed police swooped on a house in Henlow on Sunday after calls that a man had a knife.
A number of officers, included armed police, were called out to Whitworth Jones Avenue at around 10.55am.
A man was found with serious injuries at the property.
An eye witness said he heard police shouting and believed there were about six armed officers at the scene.
“There were white suits all over the place yesterday afternoon,” he said.
“It was a bit crazy.”
The ambulance and an air ambulance were called and the man was taken to Lister Hospital by land ambulance where he is in a serious but stable condition.
An investigation has been launched and enquiries are on-going.