On Thursday, 3 retired firefighters who worked at Ground zero have died on the same day due to 9/11-related illnesses, said the Fire Department of New York. The reminder on Sept. 11 is quite astonishing. It appears that the 9/11 attacks are still claiming lives, and this Monday it's the lives of 3 retired firefighters who contracted cancers after working at Ground Zero.

Retired Lt. Howard Bischoff and firefighters Robert Leaver and Daniel Heglund suffered the devastation of 9/11-related illnesses and they died only within hours of each other on Monday.

According to CBS News, the triple loss of the 3 retired firefighters all in the same day was described by Fire Commissioner Daniel Nigro as "a painful reminder" in a statement.

Nigro said it was a "painful reminder that 13 years later we continue to pay a terrible price for the department's heroic efforts on September 11th."

According to the Associated Press, the 3 retired firefighters have worked at ground zero after the World Trade Center attacks. They assisted during the rescue and recovery efforts for the victims.

Turns out, they would become victims themselves, and will be included amongst many other people with Sept. 11-related illnesses. The AP reports that of the 3 retired firefighters, one had leukemia, one had esophageal cancer and a third had colon cancer.

Jake Lemonda, president of the Uniformed Fire Officers Association said, "On that day when first responders arrived, the air was toxic and remained toxic for many months afterward."

CBS New York reports that Heglund had spent 21 years with the FDNY and died just one day before his 59th birthday. Bischoff and Leaver on the other hand had been best friends since childhood. They reportedly grew up together in Brooklyn. Bischoff worked with the department for 19 years, while Leaver served 20.

According to the New York Daily News, the FDNY lost 343 firefighters on Sept. 11, 2001, the day Al Qaeda terrorists smashed hijacked passenger planes into the twin towers of Manhattan. In total, 2,753 people died from the attacks.

It seems that the attacks are continuing, albeit indirectly. The 3 retired firefighters who recently died all in the same day are only amongst the many who battled illnesses which many believe came from the contaminated air at the site.

The deaths of the 3 retired firefighters reportedly raise to 92 the number of service men who have succumbed to illnesses while searching for survivors. According to the NY Daily, these illnesses started after the men sifted through the rubble of the fallen skyscrapers while trying to recover bodies.

CBS News reports that the death of the 3 retired firefighters came as advocates urge Congress to reauthorize the James Zadroga 9/11 Health and Compensation Act. Named after an NYPD detective who died working at ground zero, the act provides medical treatment and compensation to those who had gotten sick from exposure to toxic air from the 9/11 attacks.

Lemonda, whose union represents fire lieutenants, captains, battalion chiefs, deputy chiefs, medical officers and supervising fire marshals in the FDNY, said fire officials had knowledge of the illnesses of the 3 retired firefighters.

Their deaths were described by Bischoff's 17-year-old son as "unbelievable."

Christian Bischoff told The News, "It's really a tragedy. September 11th is something that's affected so many people in so many ways it can never be forgotten."

Bischoff was 58 when he died from Stage 4 colon cancer. According to NY Daily, he had had worked at Ladder 149 in Dyker Heights, Brooklyn and retired in May 2003 after 19 years serving as a member of the Bravest.

Christian added, "The biggest thing for him was his sense of community. He was a big part of his Brooklyn neighborhood in Park Slope and when he took the firefighter test and got in, he progressed and joined a much bigger brotherhood there."

The son continued, "The bottom line for him was his sense of brotherhood. You can't get that from any other job."

Apparently, Bischoff had been drawn to the FDNY since his friends like Leaver joined up.

Christian said of his dad, "He taught me that anything worth doing is worth doing right."

Meanwhile, Rosaria, Leaver's widow spoke to the Daily News about the death of the 3 retired firefighters. She said, "I felt at least Robert and Howie went off to heaven together."

56-year-old Leaver retired in 2004 after 20 years serving the FDNY. He was reportedly off duty on the day of the 9/11 attacks. Still, he grabbed his gear and raced toward the burning towers to help those in need

Rosaria said, "He liked helping people, having a purpose. He was brave and had a lot of courage."

She added, "Even after he was first diagnosed with leukemia in 2003, he never wanted to be called a 9/11 victim. He would say, 'The innocent people in the towers were the victims. Don't ever call me a victim. I was a first responder.'"

Lt. Heglund served 21 years in the FDNY. His death from esophageal cancer came the day before his 59th birthday. He retired in March 2003 but was diagnosed with only two years ago.

Heglund's brother, FDNY Capt. Paul Heglund, told The News, "He suffered. He's been fighting. He put up a good fight." Heglund said he and his brother responded to the 9/11 attacks and for months even after the attacks.

He said, "We would do 24 hours on and 24 hours off back then, but after working at the firehouse, you would go down there, work 10-12 hours and then go home to show your face. Then it was back to the firehouse."

Despite battling grave illnesses, there had been no regrets from any of the 3 retired firefighters. Heglund said, "About 99.9% of us wouldn't change anything that happened. Even after 9/11 and what went on afterwards, we were firemen."

He added, "That's what we do."

Meanwhile, according to the AP, the Uniformed Fire Officers Association, which planned a news conference Thursday said, were the first responders who manifested health problems after the attacks. According to NYC Resources 9/11 Health Statistics, 99 percent of exposed firefighters, including the 3 retired firefighters who simultaneously died on Monday, reported at least one new respiratory illness.

Lemonda said, "The numbers are spiking. We have over 850 firefighters and fire officers, active or retired, who have been diagnosed with 9/11-related illnesses."

Funerals for two of the 3 retired firefighters are scheduled for Friday - Leaver and Heglund. According to CBS News, the service for Leaver will be held at Francis of Assisi Church in West Nyack at 10 a.m. while Heglund's funeral will be held at the Centerport Volunteer Firehouse at 10:30 a.m. Bischoff funeral meanwhile will be held at 11 a.m. Saturday at St. Aloysius Church in Jackson, N.J.