Deborah Bonacasa was unable to hold back tears Monday as she and her 5-year-old daughter Lily stepped into their new home in Sound Beach, where the pair will forge a new life without her husband — who was killed in Afghanistan last December.

“My mom’s crying again,” Lily said as she inspected her new bedroom, painted in baby blue, her favorite color.

“They are tears of joy,” said Bonacasa, 34, an Air Force veteran. “It’s a bittersweet moment.”

Bonacasa and her late husband, Staff Sgt. Louis Bonacasa, 31, a Coram native, had hoped to begin a new chapter in their lives when he returned from his tour in Afghanistan, his fourth overseas deployment.

But on Dec. 21, a suicide bomber on a motorcycle pulled up next to Bonacasa‘s New York Air National Guard unit on patrol outside Bagram Airfield in northwest Afghanistan and detonated himself, killing Bonacasa and five other airmen.

The couple had planned to have a second child, open a smoke shop and buy their first house with the Veterans Affairs home loan for which they had been approved.

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Monday, Deborah “Dee” Bonacasa and her daughter moved into the two-story split ranch on Tyler Avenue, one of two houses that developer Mark Baisch recently built for returning veterans and sold at reduced prices.

The three-bedroom house has hardwood flooring throughout, and the kitchen comes with custom cabinets and stainless steel appliances.

The house, which would normally go for $350,000, was sold to Bonacasa for $200,000, Baisch said. He and his employees at Landmark Properties donated $50,000 to Bonacasa.

“I never had to serve,” said Baisch, 61, of Port Jefferson, whose uncle served in World War I and whose father served in World War II. “This has been kind of my way of paying it back.”

The second house, next door to Bonacasa’s, was sold for $250,000 to Megan Johnson and Joshua Johnson, who served in Iraq, Afghanistan and Kuwait as part of Air Force’s security police.

“To be here and see the magnitude of love and appreciation, and generosity, is, honestly, just — it blows you away,” said Megan Johnson, who grew up in the neighborhood.

The steep discounts were made possible by a group of people — county and town governments, private industry and neighbors — working together toward a common goal, Baisch said.

Only one house could’ve been built on the lot of 72½ feet by 100 feet, Baisch said. Suffolk county and the Town of Brookhaven agreed to allow two houses to go up, and the neighbors did not object, Baisch said. They came out in support of the idea.

More than 30 subcontractors who work with Baisch also donated material and services. In the four years that Baisch has been building homes for returning veterans, he has built a total of 10 houses so far.

“Our subcontractors constantly give on these projects,” Baisch said. “So, to them, I owe an incredible debt of gratitude.”