(CBS) – A new book is causing shockwaves through the NFL with a behind-the-scenes look at the New England Patriots’ dynasty. Within the pages of It’s Better To Be Feared: The New England Patriots Dynasty And The Pursuit Of Greatness, author Seth Wickersham shares the story of a heated exchange between then-New York Jets head coach Eric Mangini and Patriots’ head coach Bill Belichick.

An excerpt from Wickersham’s book details the event which took place at dinner during the league’s 2008 meetings.

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“At the 2008 league meetings, Belichick and then-New York Jets head coach Eric Mangini nearly had a fistfight. After a dinner for head coaches, Julie Mangini, wife of Eric, bumped into Belichick and said hi, trying to ease tension after the post-Spygate fallout. Belichick blew her off, and when she told Eric what had happened, he charged across the room and needed to be held back by other coaches from swinging at Belichick. ‘Hey Bill, F– you!’ Mangini yelled.”

Going back in time a bit, Mangini got his start in the NFL under Belichick. The two initially met when Mangini was a ball boy for the Browns. Belichick took a liking to Mangini’s work ethic and helped him get a job as an offensive assistant in Cleveland for the 1995 season. A few years later when Belichick was named defensive coordinator for the New York Jets under head coach Bill Parcells, Mangini was brought along as a defensive assistant.

In the year 2000 when Belichick left the Jets to become the head coach of the Patriots, after famously snubbing New York by writing his resignation on a napkin, Belichick again enlisted Mangini’s services by making him a defensive backs coach on his new staff. Mangini would serve as defensive backs coach in New England for five years before being promoted to defensive coordinator in 2005.

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Mangini accepted an offer to return to the Jets in 2006, this time as head coach. He was just 35-years-old when he took over Gang Green and became the youngest head coach in the NFL. In his first season, Mangini lead the Jets to a 10-6 record and ended up playing Belichick and the Patriots in the first round of the playoffs, a game New England won 37-16.

Mangini’s sophomore season was not as successful as the Jets went just 4-12 in 2007 including a Week 1 loss to the Patriots by a final score of 38-14. After the game, Mangini alerted league officials that the Patriots had illegally filmed the Jets’ defensive signals, which was the catalyst for the “Spygate” scandal.

After having the whistle blown on him by his former protégé, Belichick was disciplined by the NFL and hit with a $500,000 fine, the largest in league history at the time. The Patriots organization was also fined $250,000 and stripped of its first-round pick in the 2008 draft.

The relationship between Mangini and Belichick was forever altered by Spygate, which lead to the fiery exchange detailed in Wickersham’s book.