He is believed to have suffered a heart attack,
The 35-year firefighter rose through the ranks to become one of the ranking members of the department.
"He was a great firefighter and a tremendous leader," Chong said.
His father, Joseph Delanoy, served in the Fire Department for 35 years, and his son, Christopher, is a White Plains firefighter, Chong said.
Delanoy's wife, Joanne, has worked for the city for more than 20 years.
"This itself tells you something about William Delanoy and his legacy," Chong said. "The Department has suffered a great loss, and I have lost a confidant and a personal friend."
Click here to follow Daily Voice White Plains and receive free news updates.