Al Capone was immediately suspected of orchestrating the Massacre, although he was conspicuously living in Miami Beach, Florida, at the time.

Suspects were identified and a few individuals were arrested — including Capone bodyguard “Machine Gun” Jack McGurn — but authorities could not build a good case against anyone and no prosecutions occurred.

A leading account has McGurn setting up the Massacre by tricking the Moran gang members into showing up at the Clark Street garage to take a delivery of Canadian whiskey hijacked from Capone. But others, including Moran himself, disputed this storyline.

The police charged McGurn in the Massacre but he provided an alibi. He said he was in a hotel with his girlfriend, Louise Rolfe, the entire day. Then he married Rolfe, which allowed her to avoid having to testify against him. The press dubbed Rolfe the “Blonde Alibi.”