UPDATE (Dec. 24, 3:09 p.m. EST) -- The Rochester Democrat & Chronicle identified the deceased firefighters as Lt. Mike Chiapperini, 43, a volunteer firefighter and the Webster Police Department's public information officer, and Tomasz Kaczowka, a 911 dispatcher believed to have been in his early 20s. The shooter, who was found dead from an apparent self-inflicted gunshot, was identified by Webster Police Chief Gerald Pickering as William Spengler, 62, who served a 17-year-sentence for murdering his grandmother in the 1980s and '90s. Pickering said seven homes were burned in the fire and that the shooter's sister is missing.

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Police in small town of Webster, N.Y., are trying to figure out why four firefighters were shot by an attacker Monday morning who they say set up a “trap” for the responders to a house fire.

Two firefighters were killed, and two are being treated for serious wounds at a hospital in nearby Rochester, but they are lucid and not on life support, according to local police. An off-duty police officer was also reportedly injured.

“People who get up in the middle of the night to fight fires, they don’t expected to get shot and killed," said Pickering told NBC News, adding that the attack was apparently planned.

Gunplay like Monday morning’s ambush and Friday’s shooting spree by a mentally unstable central Pennsylvania trucker have come in the wake of a national debate over gun control following the Dec. 14 Sandy Hook Elementary School massacre in Newtown, Conn.

In the Christmas Eve incident, firefighters responded around 6 a.m. to a fire amid a group of mostly vacant seasonal homeson the shore of Lake Ontario. Shortly after arriving, the responders came under fire and were forced to retreat.

Pickering said the shooter is dead, but declined to provide any further details about what investigators now suspect could have been a planned ambush.

The Monroe County Sheriff’s Office said Monday morning that the firefighters had to retreat from battling the fire after shots rang out. They were forced to let the blaze spread over four homes.

The shooting comes three days after a man went on a rampage in central Pennsylvania, One of the injured firefighters was able to flee in his vehicle.

The latest high-profile shooting comes after central Pennsylvania residents Kimberly A. Scott, William Rhodes and Kenneth Lynn were murdered by a man who went on a seemingly random shooting spree. Police later took down the man in a shootout on a rural road.

The murderer was identified as Jeffrey Lee Michael, a truck driver who was known to fire his guns into the air and was recently obsessed with end-of-the-world predictions related to the fabricated Maya calendar prophesy, according to neighbors who spoke to CBS News.