A funeral was held in Rochester, N.Y., Monday morning for Tomasz Kaczowka, a 19-year-old volunteer firefighter killed when a sniper opened fire on a group of first responders on Christmas Eve.

Two firefighters were killed and two others were seriously injured in the shooting, which is believed to have been a trap set up by a man who deliberately set his house on fire, then reported the blaze to authorities, only to open fire as rescue crews arrived to battle the blaze.

Hundreds of mourners, including many uniformed firefighters from across the U.S. -- and from as far away as Ottawa and Toronto -- attended the funeral at St. Stanislaus Church in Rochester.

The emotional ceremony began with a bagpipe procession at 10 a.m. local time Monday. After the procession, Kaczowka's flag-draped casket was carried into the church after arriving atop a fire truck.

Kaczowka was remembered by the officiant at the ceremony as a man of faith who gave his life in service.

"We honour Tomasz today for who he was, what he did and we hold him in the highest esteem for his courage in the line of duty," he said.

In an emotional address, Kaczowka's older brother Dariusz admitted that he was often annoyed by his brother's commitment to firefighting, saying his pager often interrupted family functions and he rarely saw his brother, who would spend most of his spare time at the fire hall or 911 centre.

"I knew my brother was always an active, hands-on individual so I knew this was a way to keep him busy but I never understood its place in his life," Kaczowka said. "I now know this is so much more than a hobby. This is what Tomasz loved, and what Tomasz wanted and needed to do."

A funeral was held Sunday for the other firefighter killed in the ambush: 43-year-old Police Lt. Michael Chiapperini, who was also a volunteer firefighter.

Among those attending both funerals were nearly 100 firefighters with Toronto Fire Services. The Toronto team left for the funerals in two separate groups on Saturday and Sunday.

Capt. Mike Ogle of Toronto Fire Services said it's not uncommon for firefighters and police officers to travel out of town to pay their respects to fallen colleagues.

"It's something we've always done when something like this happens," he told CP24 on Sunday. "These firefighters from our association are heading down on their own time."

Ogle added: "You're going to see a huge contingent of firefighters and police officers there."

Among the funeral attendees from Toronto Fire Services were members of its pipe and drum band, which is said to be affiliated with Webster's fire department.

As North American firefighters mourn their fallen colleagues, police continue to investigate their deaths.

Police allege that accused gunman William Spengler deliberately set his house on fire in order to set up an ambush for the firefighters. Spengler was shot to death during the incident, but it isn't clear whether he was shot by police, or turned his gun on himself.

Last Friday, authorities announced that a 24-year-old woman had been charged in connection with the purchase of guns used in the alleged ambush. Police have charged Dawn Nguyen of Greece, N.Y. with making a false statement in connection with the purchase of a semiautomatic rifle and shotgun used that day.

Due to his criminal past, Spengler was not allowed to own firearms.

Police assert that Nguyen, who used to live next door to Spengler, purchased the weapons in 2010 on her former neighbour's behalf.

Two other firefighters wounded during the ordeal, Joseph Hofstetter and Theodore Scardino, are said to be on the mend after having their conditions upgraded to "satisfactory" last week.