U.S. Senator Frank Lautenberg, who was the oldest current senator, died today at the age of 89. His office said he died early this morning at New York – Presbyterian Hospital / Weill Cornell from complications of pneumonia. Lautenberg was the last remaining senator who served in World War II. He served in the U.S. Army Signal Corps from 1942 to 146.

Frank Lautenberg

He announced recently that he was planning to retire in January 2015 when his current term ended. He was not planning to seek re-election the following year. Newark Mayor Cory Booker had rapidly become the favorite to replace him, according to The Washing Post’s Aaron Blake.

New Jersey Gov. Chris Christie will appoint Lautenberg’s replacement temporarily.

Frank Lautenberg’s Recent Health Problems

Lautenberg has battled a number of health problems in recent years, including stomach cancer. According to USA Today’s Catalina Camia, one of his most recent problems was muscle weakness and fatigue in his legs. He struggled with that for at least a month but returned to Capitol Hill in April to vote on gun violence prevention legislation, which has been one of his main focus areas.

He entered the Senate in a wheelchair to voice his support of the bill, which expanded the background checks that are required for those who wish to purchase firearms. That bill ended up failing, as did his amendment to add a 10-round limit to ammunition clips, which he attempted to put through on the same day as the other bill.

Frank Lautenberg’s Political Career

Frank Lautenberg started serving his first term at the age of 58 following a career in business. He initially served just three terms and then retired, but he decided to run again in 2002 after Sen. Robert G. Torricelli decided at the last minute that he would not run again. Lautenberg won Torricelli’s seat and was re-elected in 2008.