A fight broke out between two police groups in the US, after a major failure of communication.
A group of Detroit police attempted to arrest a group of 'drug dealers' - who were actually police, conducting an undercover operation.
Police Chief James Craig said the fiasco is "one of the most embarrassing" events to ever happen to the police department.
The police posing as drug dealers were from Detroit's 12th precinct, while the 11th-precinct officers were preparing to execute a search warrant on a house nearby.
When the 11th-precinct officers saw the undercover drug dealers, one of them pointed a shotgun and told them to put their hands on the ground, Mr Craig said.
Shortly afterwards, when the 11th precinct tried to raid the house nearby, everything turned to chaos.
Mr Craig said the two groups "engaged in arguing, pushing and shoving... one officer grabbed another, putting him in a headlock and followed with punches, as the officer was breaking away," according to Michigan Live.
Mr Craig said the incident resulted from a lack of communication, with the 12th precinct failing to notify the 11th precinct that an operation would be happening in its area.
The 11th precinct could have then told its officers that an undercover operation was scheduled for that night.