Brian Branch Price / AP, file

New Jersey Assemblyman Alex DeCroce became the GOP's leader in the Assembly in 2003.

TRENTON, N.J. -- The Republican leader of the New Jersey Assembly collapsed and died at the Statehouse late Monday, the final day of the legislative session.

Assemblyman Alex DeCroce, 75, collapsed in a men's room around 11 p.m. and was pronounced dead at the scene.

Assemblyman Herb Conaway, the Legislature's only physician, attended to DeCroce at the scene. Gov. Chris Christie, a fellow Republican and personal friend of DeCroce for 20 years, confirmed the death 2 ½ hours later.

"Tonight I lost a dear friend, colleague and mentor," Christie said in a statement. "He helped to give me my start in elective politics in Morris County in 1993. He was one of the most kind, considerate and trustworthy people I have ever had the pleasure to know. This is an enormous loss for our state and for me personally."

The lawmaker's sudden death threw into turmoil the Legislature's reorganization plans for Tuesday and caused Christie to delay his annual state-of-the-state address. The Assembly and Senate greatly scaled back swearing-in ceremonies for new members. Christie planned to deliver remarks about DeCroce on the floor of the Assembly in lieu of his scheduled address.

DeCroce's death shocked lawmakers and legislative staff who had been working with him all evening as the Legislature wrapped up its session with a flurry of last-minute bills. One of his final acts as the GOP leader was to accuse Democrats of casting votes for an absent member.

An obviously emotional Christie returned to the capital around midnight, wearing a sport jacket over a T-shirt and loafers but no socks.

The governor was seen breaking down while embracing Assembly Speaker Sheila Oliver and other legislative leaders.

Michael Drewniak, a spokesman for Christie, told the Star-Ledger that DeCroce "was the state's finest elder statesman."

'Terrible and shocking loss'
Oliver and incoming Majority Leader Lou Greenwald, both Democrats, issued a joint statement.

"The Assembly and the State of New Jersey has been struck by a terrible and shocking loss," they said. "Alex DeCroce was a friend, colleague and leader. He was a dedicated public servant. He was a true New Jerseyan. He was always someone ready with a handshake and a laugh, no matter the circumstance, and his devotion to the people of New Jersey was unwavering. The Assembly has lost one of its great institutions."

DeCroce's body, covered and placed on a stretcher, was removed from the ground floor of the Statehouse about 12:40 a.m.

The lawmaker, from Parsippany-Troy Hills, served in the Assembly since 1989 and became the GOP's leader there in 2003.

His district includes parts of Morris and Passaic counties.

He was also president of a Parsippany real estate company.

His wife, Betty Lou DeCroce, is a deputy commissioner with the Department of Community Affairs.

The Associated Press and msnbc.com staff contributed to this report.