Updated

For the men and women who earn a living by rushing into hazardous situations to help, the Christmas Eve ambush of two firefighters in upstate New York was a chilling reminder of how unpredictable the dangers of the job can be.

Mike Chiapperini and Tomasz Kaczowka, volunteer firefighters of the West Webster Fire Department, were gunned down by William Spangler, who had set his family’s home ablaze as a sick trap for those selfless and brave enough to come to his rescue. What prompted Spangler, who killed himself, to hatch the diabolical plan may never be known. But it gives firefighters and medics everywhere something else to consider when responding to calls for help.

“If a police officer shows up, he or she is likely going to arrest someone and usually deals with some sort of altercation. When a firefighter or a medic shows up to a scene, it's to save lives,” Peter Matthews, a firefighter and editor for Firehouse.com told FoxNews.com. “When you arrive at a scene you are thinking about so many different things; the last thing you would expect is gun shots.”

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In a recent survey of 256 firefighters and emergency medical workers from throughout the U.S., more than 48 percent said that they had been physically assaulted at least once while on duty. Experts estimate that there are 700,000 assaults on paramedics and EMTs every year, and the National Fallen Firefighters Foundation lists assaults as one of the top 16 safety issues that firefighters face when responding to calls.

And shooting incidents are not altogether uncommon:

- In March 2011, Justin Angell, a 20-year-old firefighter from Long Island, N.Y., was shot when he responded to a call about a car that had struck a utility pole. As he approached the car, one of its occupants opened fire. Angell was hit in the hip and recovered.

- In 2004, Brenda Denise Cowan, a fire lieutenant from Lexington, Ky., was shot to death while aiding another shooting victim lying on the side of a road. The husband of the victim she was trying to help was charged with both shootings.

- In July 2008, Ryan Hummert, a firefighter in Maplewood, Mo., was shot to death when he responded to a call of a car fire that was deliberately set by the shooter as a trap.

- An incident eerily similar to West Webster occurred in 1977 in the Pennsylvania town of Shippensburg, when Fire Chief James Cutchall responded to a cabin blaze and was fatally wounded by sniper fire. Other firefighters responding soon after Cutchall were also greeted by a hail of bullets, which wounded Deputy Chief Robert Monn and 18-year-old Scott Riechenbach.

The problem for firefighters and medics, said Billy Goldfeder, a nationally recognized expert in firefighter survival and operations, is that the hidden dangers cannot influence how they go about their jobs. Chiapperini and Kaczowka did what any firefighters would do, he said.

“Every fire department that I know of would of handled it the same way,” said Goldfeder, who is deputy fire chief for the Cincinnati suburb of Loveland-Symmes. “Those responders in West Webster are us. Any one of us could have done the same thing.

“The West Webster firefighters did everything right. How would they have been able to seen a sniper ready and waiting for them? It was early in the morning and dark, plus they had a smoke condition.”

Goldfeder says that many fire departments across the country already have plans in place to prevent violent assaults on first responders. But risking their lives to save innocent civilians will always leave first responders exposed to the evil plans of monsters like Spangler.

“All firefighters are aware of the possibilities, but when we respond, our main focus is saving lives,” he said. “We don’t go in with blinders on, but our main concern is helping others.”