A little girl who was born three years after her father was killed in the line of duty, has celebrated her birthday with members of the NYPD.

Angelina Liu turned four on July 25. Her at-home, mermaid-themed party had the NYPD Blue Knights motorcycle group in attendance for the second year in a row, mom Pei Xia Chen Liu, also known as Sanny Liu, told Fox News.

Angelina Liu, daughter of NYPD cop Wenjian Liu, celebrates her fourth birthday July 25, 2021.

Angelina Liu, daughter of NYPD cop Wenjian Liu, celebrates her fourth birthday July 25, 2021. (Pei Xia Chen Liu)

"She has his mannerisms, his personality – she’s very caring," Chen Liu said. "[And] she just looks like her daddy. I always feel like her daddy is with us. He was never gone."

Chen Liu continued, "She’s also the connected between me and my husband and she is also the hope. My in-laws are so, so happy there’s a child to carry on the Liu last name because [their son] was the only child."

NYPD Detective Wenjian Liu, 32, was assassinated in his car along with his partner, Rafael Ramos, 40, in Brooklyn’s Bedford-Stuyvesant neighborhood on Dec. 20, 2014, Fox News previously reported. The attacker, Ismaaiyl Brinsley, killed himself nearby with other officers in pursuit.

Chen Liu said she and Liu met at a party in Brooklyn and were together for seven years. The couple wed Sept. 19, 2014 and had been married just three months when Liu was killed.

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Chen Liu said she requested her late husband’s sperm be preserved and two years later, in 2016, she underwent in vitro fertilization (IVF).

Chen told Fox News she wanted to wait to undergo the IVF process until she was "physically and mentally ready," as she was grieving Liu’s death. 

Angelina Liu, daughter of Sanny Liu and NYPD cop Wenjian Liu, celebrates her fourth birthday July 25, 2021.

Angelina Liu, daughter of Sanny Liu and NYPD cop Wenjian Liu, celebrates her fourth birthday July 25, 2021. (Pei Xia Chen Liu)

"That’s all my husband talked about was having a family and raising kids together. That was our dream," Chen Liu said. 

"The night he died, that’s the only thing that came to my mind," she added.

The IVF process was a success, thanks to Dr. Pak Chung and his team at Weill Cornell Medicine, and Angelina was born on July 25, 2017.

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Angelina Liu, daughter of NYPD cop Wenjian Liu, celebrates her fourth birthday July 25, 2021.

Angelina Liu, daughter of NYPD cop Wenjian Liu, celebrates her fourth birthday July 25, 2021. (Pei Xia Chen Liu)

Chen Liu said she keeps a memorial room for Liu showcasing his awards and recognition from his time with the NYPD. 

Chen Liu said the NYPD has "never left her side" since Liu’s death. 

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"They have not forgotten me and they are so happy I have Angelina," she said.

"I’m so glad my husband chose the career as a police officer and I’m so proud of what he has done…I’m sure he’s smiling down from heaven, looking down and seeing how beautiful and smart his daughter is," Chen Liu added.