The bodies of seven men were found dumped in plastic chairs on a busy roundabout in the Mexican city of Uruapan, authorities have said.
The men, thought to be car washers, had been shot in the head and some had ice picks holding placards nailed to their chests.
Threatening messages had been nailed to some of the men's chests using ice picks and the victims had all been shot in the head.
One of the placards said: "Warning: This is going to happen to all muggers, pickpockets, kidnappers, rapists and extortionists."
The bodies of the seven men - who have not been identified but are thought to have worked as car washers at crossroads in the city - were placed in sitting positions in the chairs many with their hands and feet bound and bandaging over their heads.
They were dumped on a roundabout on one of the busiest streets in the city. The motive is as yet unclear.
Residents in the area discovered the bodies outside a Pepsi bottling plant at around 5.30am local time.
It comes after seven people were killed in neighbouring Guerrero state when armed men opened fire in a bar in Ciudad Altamirano on Friday evening.
Four civilians and three off-duty federal agents were among those killed.
Both Guerrero and Michoacan on Mexico's west coast have seen a surge in violence in recent years attributed to warring drug cartels.Nearly 70,000 people have been killed in drug-related violence in the last seven years.