Mourners gathered in Queens on Wednesday to say their final goodbyes to a former NYPD detective who was a central figure in the fight to permanently fund the September 11 Victim Compensation Fund.

The funeral for 9/11 first responder Luis Alvarez, 53, took place at Astoria's Immaculate Conception Church, where his father served as a deacon for years.

Alvarez made a big difference in the last weeks of his life, trying to help others with September 11th-related illnesses. At his funeral in Astoria, his sister said he was still thinking about officers and firefighters in his final hours.

"He told me he had been walking and walking and walking," Aida Lugo said at the funeral service, joined by David Alvarez, Luis's son. "The nurse asked him where he had been walking. And with David as my witness, my brother responded, 'I was walking to find first responders, to make sure they get help.'"

Alvarez retired from the NYPD in 2010. Three years ago, he learned he had colorectal cancer. He said he contracted it after working in the toxic debris at the World Trade Center site.

(Former NYPD Detective Luis Alvarez before cancer ravaged his body).

His body ravaged by the disease and 69 rounds of chemotherapy, Alvarez traveled to Washington three weeks ago to urge Congress to replenish the federal fund for September 11th victims.

"You all said you would never forget," Alvarez said in his congressional testimony. "Well, I'm here to make sure you don't."

Alvarez died last Saturday, not long after he entered hospice care.

A House panel approved extending the life of the fund indefinitely earlier this month. A bill that would fund the Victim Compensation Fund through 2090 is expected to pass the Democrat-led U.S. House of Representatives this month. The Senate plans to take up the measure next month.

Comedian Jon Stewart, a fierce advocate for 9/11 first responders, appeared with Alvarez at the capitol and attended the funeral.

To drive home the point about taking care of first responders, Police Commissioner James O'Neill reminded people that 23 NYPD officers died on 9/11, but he said 222 officers have died from 9/11 related-illnesses since then.

"No person who responded to 9/11, or who worked to the point of exhaustion during the lengthy rescue and recovery period that followed, should ever need to beg our elected officials to act," O'Neill said. "It is in Lou's memory that we must strenuously urge all our representatives to recognize that the Unites States of American cannot in good conscience place a financial cap limit or temporal limit on this slow-moving crisis."

Officers from various departments attended the funeral.

"I think one word is the way to put it: courageous. Courageous and a fighter," Mark Lobel, of the Pender County, North Carolina, Sheriff's Office, said about Alvarez.

"Louie could have spent his last days and weeks and hours with his family and loved ones," said John Feal of the Feal Good Foundation. "He chose to spend it making a difference."

Something Alvarez did as a Marine and an officer. His son David says he hopes to follow in his dad's footsteps and join the NYPD.

"Before he became an American hero, he was mine," David Alvarez said. "He was my hero, my inspiration."

At his wake on Long Island on Tuesday, family and friends said Alvarez wouldn't stop fighting no matter how sick he became.

Alvarez's family said he wasn't only concerned about first responders, and he wanted to make sure sick construction workers — as well as all the people who lived, worked, and went to school in the World Trade Center area — were cared for.