An NYPD cop assigned to Staten Island died unexpectedly from a mysterious medical issue last week, leaving behind a husband and young daughter, according to her grieving dad.

Officer Brittany Gromadzin, 29, had been undergoing treatment and tests to diagnose an “unknown” ailment for close to a year, but lost her battle early Nov. 14, wrote dad Jim Kelly on Facebook.

Just days earlier, “She was telling me about her planning of Christmas gifts & ideas for the whole family,” over a FaceTime chat, wrote Kelly.

But late on Nov. 13, the four-year veteran assigned to the island’s 121st Precinct was rushed into a local hospital.

“Our family was with Brittany during her final hours in the hospital,” wrote Kelly, calling the death “totally unexpected.”

“We all remain in shock, we are heartbroken & in total disbelief.”

In addition to a husband, Jon, the cop leaves behind an 8-year-old daughter, according to the post.

“Her daughter Gianna was her whole life & joy,” Kelly wrote. “[She] loved family & friends.”

Well over 100 uniformed officers attended Gromadzin’s funeral Monday at Holy Child Church in the borough’s Annadale neighborhood, according to the Staten Island Advance.

Gromadzin’s hearse was escorted to the church by department motorcycles, and fellow officers served as pallbearers, the report said.