NEW YORK (CBSNewYork) — More help is on the way for the families of the NYPD officers who were gunned down in December as they sat in their patrol car.

The Stephen Siller Tunnel To Towers Foundation has already paid off the mortgage on the home of Officer Wenjian Liu‘s family. Now it is replacing the leaky roof, siding and windows and installing central air conditioning, WCBS 880’s Marla Diamond reported.

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“We’re extremely grateful and overwhelmed by everyone’s kindness, gratitude and generosity,” his widow, Pei Xia Chen, said at a news conference outside her Gravesend, Brooklyn, house on what would have been Liu’s 33rd birthday.

Work on the home will begin soon. Liu’s widow, father and mother live at the house, 1010 WINS’ Mona Rivera reported.

The foundation is doing the same for the family of Liu’s partner, Officer Rafael Ramos.

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Officers Rafael Ramos and Wenjian Liu, who were killed in their patrol car on Dec. 20, 2014. (Credit: NYPD)

Officers Rafael Ramos and Wenjian Liu, who were killed in their patrol car on Dec. 20, 2014. (Credit: NYPD)

“We’re here saying to you that we haven’t forgotten,” said Frank Siller, the group’s president.

Liu and Ramos were fatally shot inside their car in Bedford-Stuyvesant, Brooklyn.

The shooter, Ismaaiyl Brinsley, killed himself shortly after the brazen daytime ambush.

Investigators say Brinsley was an emotionally disturbed loner who had made references online to the killings this summer of unarmed black men — including Eric Garner on Staten Island — at the hands of white police officers, vowing to put “wings on pigs.”

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The Stephen Siller Tunnel To Towers Foundation, named for a firefighter killed on 9/11, collected more than $1 million in donations from across the country and other parts of the world in an effort to pay off the families’ home mortgages.