Date: November 1974
Manner: McGonagle, leader of the Mullen Gang, was found shot to death and buried at Tenean Beach in Dorchester.
A former Bulger associate claims Bulger, who then worked as an enforcer for a rival gang, killed McGonagle's younger brother after mistaking him as the Mullen Gang leader. This prompted a mob war, leading to the gangs merging with Howie Winter as their overall leader. McGonagle was killed two years later. His body was found buried in 2000 near Tenean Beach.
McGonagle was married to Margaret McCusker, the sister of Bulger's longtime girlfriend, Catherine Greig.