(WBBM) – A disgraced former Berwyn police officer says he was the key to a robbery gang. The details came out during testimony in the racketeering trial of a former alleged mob boss.

LISTEN: Newsradio 780’s Dave Berner Reports

READ MORE: Frank Pietrangelo, Hero Of 1991 Stanley Cup Playoffs, Says He Was Among Those Sexually Abused By Hockey Coach Tom 'Chico' Adrahtas

James Formato joined the Berwyn Police Department in the mid-90s. He said he wanted to do a good job, wanted to help people. But by 2003 he was robbing the same people he said he wanted to help.

Testifying for the prosecution in the trial of Michael “The Large Guy” Sarno, Formato says he would make his police calls to homes in Berwyn during the day, and then burglarize the same homes at night. One place was the home a drug dealer he hit so often it was nicknamed “The ATM”.

Formato was introduced to the alleged Sarno street crew by his father. He later became a valuable resource for the gang, frequently acting as a lookout — at times even while on duty.

READ MORE: Shane Jason Woods Of Downstate Auburn, Illinois Charged In Jan. 6 Capitol Insurrection

Sarno’s racketeering trial offers peek into the inner workings of Chicago-area organized crime, laid low by prosecutions that sent older mobsters to prison for life.

In Chicago, the mob now focuses more heavily on running illegal video gaming, with approximately 25,000 machines in bars and restaurants, generating millions of dollars in revenue, according to some estimates.

It’s leaders allegedly include Sarno, who weighed as much as 300 pounds and was known for using his bulk to collect mob gambling debts as an enforcer. Bilek says he suspects Sarno may have taken over operations in the city’s western suburbs from one of the imprisoned bosses.

MORE NEWS: Police Investigate After Video Shows Man With Gun, Woman Hiding Behind Police Officer Who Seemingly Walks Away

(TM and © Copyright 2010 CBS Radio Inc. and its relevant subsidiaries. CBS Radio and EYE Logo TM and Copyright 2010 CBS Broadcasting Inc. Used under license. All Rights Reserved. This material may not be published, broadcast, rewritten or redistributed. The Associated Press contributed to this report.)