NYPD officers Wenjian Liu and Rafael Ramos died in an ambush in 2014. The tragedy of their deaths, though, has led to a move that will help protect other officers from a similar fate.

The city has set aside more than $10 million for bullet-resistant glass and doors on patrol vehicles in its draft $84.7 billion budget for the upcoming fiscal year.

On Jan 31, the NYPD demonstrated the glass and doors that will be installed on more than 3,800 patrol vehicles. The doors will be installed by the end of the year; the windows by the first half of next year, Mayor Bill de Blasio said.

"You saw that material, very high-tech material, that absorbs the bullet and literally takes the bullet's trajectory and uses it against it to stop it dead in its tracks," de Blasio said inside an NYPD training classroom.

Police Commissioner James O'Neill said the need to protect officers in vehicles from gunfire was motivated by the 2014 shooting deaths of Liu, 32, and Ramos, 40 - who were ambushed by a gunman as they sat in their patrol car in Brooklyn - and the killing the following year of Brian Moore, 25, fatally shot in his unmarked squad car by a suspect in Queens.

The deaths of Liu and Ramos just before Christmas in 2014 stunned the city and came at a time of polarization between police and members of African-American communities across the US, with several incidents of black men dying in confrontations with police, including one in New York. Eric Garner died when he was wrestled to the ground on Staten Island.

Liu and Ramos' killer, Ismaaiyl Brinsley, 28, claimed on social media that he was targeting police to avenge the deaths of Garner and Michael Brown in Ferguson, Missouri, in the summer of 2014.

Liu, a native of South China's Guangdong province, came to the United States at age 12 with his parents. He decided to be a police officer after the 9/11 terrorist attacks in 2001, and joined the NYPD in 2007.

In June 2015, de Blasio and then-police commissioner William Bratton attended the unveiling ceremony for "Detective Wenjian Liu Way" in Gravesend, Brooklyn. Also in attendance were the officer's parents and widow, Peixia Chen, along with survivors of Detective Ramos and dozens of police officers. Both Liu and Ramos were posthumously promoted to detective.

Their funerals drew more than 20,000 police officers from around the country.

Liu lived in the neighborhood with his wife, Peixia Chen, and also had bought a home nearby for his parents, mother Xiuyan Li and father Weitang Liu.

"Our law enforcement officers sacrifice their lives day in and day out, in serving and protecting this great city. This city is our home," Chen said at the ceremony.

The news about the bullet-resistant glass and doors came on Jan 31 when the mayor and the Patrolmen's Benevolent Association (PBA) President Patrick Lynch announced a tentative contract agreement covering 23,810 NYPD employees.

"This agreement provides the compensation and benefits the world's finest police department deserves, while outfitting the entire force with body cameras and delivering the transparency and policing reforms at the center of effective and trusted law enforcement," de Blasio said.

As part of the deal, the PBA agreed to drop body camera litigation against the city, and the NYPD can expand the use of body cameras to the entire workforce - a step forward for police accountability and transparency.

All patrol officers will be outfitted with cameras by the end of 2019.

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