In 2077, Captain Jonathan Widmark and his Boston Police Department task force launched an official investigation on the mob boss, code-named "Operation Winter's End." During this investigation, the extent of Winter's crimes were revealed. He was involved in almost every type of crime, ranging from petty larceny to first degree murder. It was suspected, though not proven, that Winter was behind the murder of the fiancée of the lead detective, Ms. Jennifer Lands, in August 2077. Around October of that year, the Boston Police Department closed the case against Winter. This was done due to Winter's deal with the BADTFL to incriminate his associates. His cooperation with the district attorney granted him immunity from prosecution for his crimes.
Eddie Winter willingly became a ghoul through a radiation experiment to obtain eternal life. His choice of life as a criminal eventually catches up to him.
The following is based on unverified behind the scenes information and has not been confirmed by canon sources.
Eddie is most likely the Fallout universe's parallel to real life kingpins James Joseph Whitey Bulger Jr. and Howard Thomas "Howie" Winter, both of whom once led Boston's infamous Winter Hill Gang. Like Eddie, Whitey Bulger led a prosperous criminal empire before suddenly disappearing around Christmas in 1994. Bulger remained at large for 16 years until his arrest on June 22, 2011 in Santa Monica, California. He was found guilty of multiple counts of racketeering, money laundering and murder (among other charges) on August 12, 2013. Bulger's story was eventually made into a movie, Black Mass, starring Johnny Depp as Bulger.
End of information based on unverified behind the scenes information.