Dad of Boy Found Covering Brother in Deadly Fire Says Seeing Heartbeat Was 'Most Painful' Before Organ Donation (Exclusive)

3-year-old Zachariah and 6-year-old William Brice died following a house fire — now, their organ donations could save many other lives

The parents of two boys who died of smoke inhalation in a house fire in Northern Virginia last week say their legacy will impact dozens of lives — and even save some, as their organs have now been donated to allow for transplantation to other children.

"The doctors said their organs were still strong," the boys' father, James Brice, tells PEOPLE in an exclusive interview.

"That was the most painful thing to see for us — we could still see their heartbeats on the screen and their vitals but there was no brain activity because of the smoke inhalation."

Three-year-old Zachariah and 6-year-old William were unresponsive for 45 minutes after firefighters pulled them from the house fire in their grandparents' home. While their bodies didn't externally appear to have suffered from burns, the damage done internally was ultimately too extensive for recovery.

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While the boys' parents — father James and mother Reina — and their siblings — 13-year old Seth and 8-year-old Logan — had been "praying that they would survive the injuries," James says hearing that William and Zachariah's organs could be used to help other children offered a slight glimmer of hope.

"We're Christians and we have faith and we know other people out there are praying for the miracles that we were," James says. "If we could be an answered prayer or a miracle to another family, that gave us some comfort."

So, William and Zachariah had organ donor surgery, with both boys rolled down the hallway of the hospital in a Walk of Honor while family and hospital staffed lined the hallways and cheered, "Well done, you did it," over and over.

As James explains, the young boys' organ donations make them heroic well beyond their years — though that was obvious to all who knew them.

James tells PEOPLE that, while the boys were in the hospital, the family was visited by the team of firefighters who responded to the blaze.

"They told us that when William and Zach were found, William was actually covering and protecting Zachariah like a shield," James explains. "We knew that to be his character because that's just who he is. He, himself, is a hero."

Upon delivering the news to the family, the firefighters then gave the boys firefighter medallions on the spot, naming them honorary firefighters from their hospital beds.

That the boys died side by side, says James, was not surprising considering their close bond.

"Zachariah was always following William everywhere and William was so proud. He would tell everyone, 'That's my baby brother,' " James says.

Now, James says the family finds itself in "uncharted waters," unmoored by the loss of William and Zachariah and navigating the accompanying grief and shock.

"Losing them both at the same time was really, really tough," James says. "Seth, our teenager, is trying to be stoic and strong but then he'll have moments of anger or questions or tears. Logan, our 8-year-old, is wondering who's gonna play flag football with us in the backyard now?"

Despite the sadness, James says he and Reina want to focus on the heroism of their sons, and the joy they brought to so many people. With that in mind, an upcoming memorial service (one with space to seat the thousands expected to attend) is being called "a party," James says, in an effort to feel "fun and festive."

"We are balancing the grief of missing them and at the same time proud that our 6-year-old made such a heroic choice," James says. "Through the organ donations, we are also hopeful that another family will get to experience a miracle thanks to our boys."

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