The group were relaxing in a pool hall in Temixco, southern Mexico, when 20 armed men stormed the building.
They led the four men out into the street and shot them dead at about 1.30pm.
The body of one of the men gunned down in Temixco, southern Mexico, lies under a sheet as two policemen stand guard
Grief: A woman tries to get past police at the scene of the killings
State police, soldiers and federal agents were sent to the scene which they cordoned off for investigations to begin.