HBO documentary Marathon: The Patriot's Day Bombing shows the grueling path to recovery and normalcy for survivors including newlyweds Jessica Kensky and Patrick Downes
Allana Taranto/Courtesy HBO
Credit: Allana Taranto/Courtesy HBO

Patrick Downes and Jessica Kensky had only been married for seven months when they headed to the finish line of the Boston Marathon on April 15, 2013, to cheer on the runners.

But then two homemade bombs exploded, killing three and wounding countless others at the race — including Downes and Kensky, who have had “30 to 40” surgeries on their limbs (and even their ears, which were ruptured in the explosions).

“The bombing did not leave one part of our lives untouched,” Kensky tells PEOPLE.

“When you get married, you’re on this high,” she says. “You feel unstoppable. You have so many hopes and dreams and goals.”

Their wedding vows took on a new meaning after the bombing, she says: “When we said our vows and said, ‘In sickness and in health,’ we thought that would be way down the line — not so soon after we got married.”

Kensky, 35, lost her left leg below the knee and later had her right leg amputated. “When I’m back in Boston and in a wheelchair after surgery, people don’t think it was because of the bombing, because that was so long ago,” she says. “They think, ‘Surely you’re walking now with a prosthetic.’ ”

Now Kensky and Downes, who also lost his left leg below the knee, will share their story — their joy and struggles, their relationship and their dog — in HBO’s documentary Marathon: The Patriot’s Day Bombing, airing Monday night.

The gritty, resonant film details the emotional and physical challenges survivors and their families have faced, and continue to face, in the years since the deadly terrorist attack.

“It’s far more complicated than we ever imagined it would be,” says Downes, 33, who just earned his doctoral degree in psychology at William James College in Newton, Massachusetts. “Every day has been a struggle for us. It’s not like you just put on a prosthetic and you’re done.”

As Marathon co-director Annie Sundberg told PEOPLE, “We wanted to tell the story of these survivors — the resiliency and the strength — but also that it’s not always a pretty picture or a Hollywood ending.”

RELATED VIDEO: Marathon: The Patriot’s Day Bombing Exclusive Trailer

‘This Really Rocked Our World’

“I’m really shocked that I’m not at least out of the initial surgical phase yet,” says Kensky. She will have another surgery in the next month or so.

“I don’t walk with any regularity,” she says, “because something will happen, and I will have another surgery and then be in a wheelchair for six to eight weeks without a prosthetic.”

After the bombing, as Downes and Kensky watched other young couples buy houses and start families, their lives filled up with doctors, nurses and hospitals. On Aug. 25, 2014 — their second wedding anniversary — they moved into the Walter Reed National Military Center in Bethesda, Maryland. “Our treatment has been so intensive that it was best for us to stay here,” Downes says.

Kensky misses the daily routine of her life before the bombing, including her job as an oncology nurse at Massachusetts General Hospital, in Boston, and running with Downes.

“We went from being this young, healthy, fit couple — I took a multivitamin everyday and that was it — to having a whole slew of doctors,” Kensky says. “We are looking at a really challenging, possibly greatly shortened life.”

Since that horrific day, they have never been able to return to the fourth-floor walk-up in Cambridge, Massachusetts, that they called home. “We couldn’t get back into the house because we were in wheelchairs,” Kensky says. “We couldn’t get into our cars. I couldn’t return to my job. Patrick lost a fellowship in California.”

“This really rocked our world,” she says.

So did Kensky’s “gut-wrenching” decision to amputate her right leg in January 2015, because it had been so severely wounded in the bombing. Making such an agonizing decision “goes against your natural instincts,” she says.

It also changes the way she remembers certain times of her life: “I’ll think back to Christmas and say, ‘Oh yeah I had legs then, that Christmas,’ or ‘Oh, I had a right leg at that birthday party. That’s right …’ ”

Courtesy HBO
Jessica Kensky (black) in rehabilitation.
| Credit: Courtesy HBO

Besides intensive physical rehabilitation, the couple also receives individual and couple’s counseling, “to help us make sense of everything,” Downes says.

It’s the work of years.

Kensky says, “I do feel older than my age.”

“It’s a struggle,” Sundberg, Marathon‘s co-director, told PEOPLE. “But in the struggle, the human spirit and strength and courage of these individuals and their families having to come together is what we found so inspirational.”

‘We Want to Shine the Light’

Their life as a married couple is not what they had hoped for four years ago, but Downes and Kensky are not despairing.

She jokes that at dinner she will ask him how his day was — “I am with him literally all day, so I know every single thing he did that day,” she says.

The couple also delight in spending time with their service dog, Rescue, an affectionate black Labrador.

“He has such healing power,” Downes says. “He has his own personality and makes us laugh, especially when he lies down and sighs.”

John Tlumacki/The Boston Globe/Courtesy HBO
Patrick Downes
| Credit: John Tlumacki/The Boston Globe/Courtesy HBO

The pup has touched their lives so much that Kensky is writing a children’s book about him, Rescue and Jessica: A True Friendship, set for release in 2018. “We are really proud of it,” Downes says. “We are hoping to use the attention we have received to celebrate all people with disabilities and celebrate the incredible and adorable work that service dogs do.”

Choosing to be filmed for the HBO documentary wasn’t easy, Downes says. But he and Kensky wanted to reveal the true course of their recovery: its ups and downs, its length.

“We think it’s really important to cover the much larger trajectory of recovery that we are still in very acutely right now,” he says. “It’s much longer than we had ever anticipated.”

Downes and Kensky also hope some good comes of their participation, especially after all the support they have received in the wake of the bombing.

“There are a lot of people who are suffering anonymously,” Kensky says, adding that she hopes Marathon helps people struggling with life’s challenges to find “the strength to continue.”

“I’m also hoping that people who haven’t been touched by something like this might be more apt to reach out to a refugee family or someone with cancer or a victim of a violent crime,” she says.

“We have received so much good will and love and support, because of how public it was, that we want to shine the light on others.”

Marathon: The Patriot’s Day Bombing premieres Monday (8 p.m. ET) on HBO.