BRAINTREE -- The last time Father Chris Keenan saw Father Mychal Judge alive was on the night of Sept. 10, 2001.

The two men, both Franciscans, were living in the same friary in New York City. In their ministry, they served homeless people and people struggling with substance abuse. Father Judge was also a FDNY chaplain.

Father Keenan had known and worked with Father Judge for decades -- it was he who inspired Father Keenan to become a Franciscan priest. The night of Sept. 10 was a typical one. Father Judge walked through the streets of New York, greeting the homeless people he had come to know. Back at the friary, he and Father Keenan prayed together.

"Good night, Chrissy," Father Judge said. "Know you're always in my heart and prayers."

The next morning, American Airlines Flight 11 flew over the friary on its fatal path into the North Tower of the World Trade Center. Father Keenan went to St. Vincent's Hospital to accompany victims of the attacks and help them reunite with their families. Father Judge joined firefighters at the World Trade Center. The final moments of Father Judge's life were immortalized by French filmmakers Jules and Gedeon Naudet in the documentary "9/11."

On the 25th anniversary of the attacks, Father Keenan, now 84, watched his friend and mentor live and die on screen yet again.

"Watching it, it's a very profound experience," he said.

He and film audiences throughout the world have seen Father Judge pray the rosary, the one he carried with him all the time.

"You could tell, the look of fright on his face, knowing the terrible reality of all of those firefighters going up," Father Keenan said.

When the South Tower fell, the ensuing storm of debris sent Father Judge's body across the lobby of the World Trade Center, right at the feet of those he served. His final act had been giving last rites to a firefighter. The footage is gray -- "Through a glass darkly," Father Keenan called it.

Officially, Father Judge was the first recorded casualty of 9/11. The photo of firefighters carrying his body from the wreckage became a modern-day Pieta, one of the iconic images of the attacks. Father Judge was immortalized among the day's heroes, a symbol of faith amid impossible horror.

"He was present to people in a way like you were the only one that existed," Father Keenan said, "whether you were Mayor Giuliani or someone struggling on a breadline."

He took Father Judge's place and served as a FDNY chaplain until 2022. For seven months after 9/11, Father Keenan was at Ground Zero searching for human remains in "the pit."

"I'm descending into hell," he said. "And I'm seeing the face of God in everyone who is down there helping in the recovery."

Even 25 years later, Father Keenan's experiences on 9/11 are not something he can fully explain. He developed 14 medical conditions, including four types of cancer, after his time at Ground Zero. Countless first responders have suffered from similar ailments.

"Certainly the focus was not on what were my feelings, or what were my needs, as much as what happened and how I might be helpful," he said.

That was what Father Judge taught him, ministering to those the rest of society had forgotten. Twenty-five years after his death, his legacy lives on at the Father Mychal Judge Center for Counseling and Recovery at St. Anthony Shrine in Downtown Boston. The center provides "pay what you can" assistance to those struggling with grief, mental illness, and substance abuse -- those who Father Judge was so close to in his life. The center turns no one away, regardless of their life or financial situation.

"Mychal himself would be thrilled about it," said Father Keenan, who was involved in the center's founding over 20 years ago.

Father Judge and Father Keenan were both formed at St. Anthony Shrine. The latter was in residence there from 1979 to 1990, which he called one of "the most significant and beautiful experiences" of his life.

"The wonderful people in Boston and the depth of their faith life" formed him as much as Father Judge had.

Abby Paine, the center's director, sees 25 of its over 50 clients, from college students to parents to senior citizens.

"It's changed me as a person," she said. "It's very humbling to sit with someone and hear the most honest parts of themselves and feel like they're trusting you to walk with them through anything."

She experiences joy and grief alongside her clients. She hears traumatic stories from their pasts, often stories no one else has heard.

"It's very emotional to be able to go back in time with them," she said, adding, "It's made me look at the world so much differently."

Father Judge's story reminds her "to never give up on anyone." She thinks of how, when everyone else was running from the World Trade Center, he went inside.

She said, "There's no one too broken for the center to help."

"I think it carries on his legacy to say that we're still doing the work he started and we're continuing to do it in his honor," she said.