UNION BEACH - A volunteer firefighter who died while fighting a four-alarm fire at a commercial building suffered a heart attack, according to Monmouth County officials.

Acting Monmouth County Prosecutor Christopher J. Gramiccioni says 54-year-old Robert Meyer collapsed after leaving a burning building Sunday evening.

Meyer, who volunteered with Union Hose Fire Co. #1 in Union Beach for eight years, was with his unit as they battled a four-alarm blaze at HydrAir, Inc. on Union Avenue.

An autopsy performed Monday showed that Meyer died from cardiac arrest. He was pronounced dead at a hospital.

The town hit hard by Superstorm Sandy is mourning Meyer, as are dozens of fellow firefighters who took to the fire department's Facebook page to leave their condolences for Meyer.  A sign outside Union Hose Fire Co. #1 said "Ultimate Sacrifice, Bob Meyer, June 8 2014."

"This is a tragedy for the family, firefighters, and the community of Union Beach," Gramiccioni says.

Meyer was also a member of the Belford Engine Company #3 of the Middletown Township Fire Department. He was a recipient of an award in 2005 from the prestigious Carnegie Hero Fund Commission for helping a state trooper save a man from a burning truck on the New Jersey Turnpike in East Brunswick. He volunteered there for more than 30 years.

Authorities say the fire appears to have started with some electrical wiring in the rear of the building.

Meyers was married two years ago, and leaves behind his wife, a brother and a sister. He had just rebuilt his home after losing it to Hurricane Sandy.