NEW YORK — At the start of her midnight shift, Officer Miosotis Familia was in a New York Police Department mobile command post, writing in her notebook, when a gunman strode toward her.

She never saw Alexander Bonds coming before he shot her in the head through the passenger-side window, killing her before officers ultimately killed him, police said.

Police are investigating what may have prompted Wednesday’s shooting, which Police Commissioner James O’Neill described as an officer being “assassinated in an unprovoked attack on cops.”

“Officer Familia was murdered for her uniform and for the responsibility she embraced,” O’Neill said in a message to officers Wednesday night. “For the NYPD, regularly achieving lower and lower crime figures means absolutely nothing when one of our own is brutally shot and killed.”

A 12-year NYPD veteran, the 48-year-old Familia had come to police work later in life than most on a force where the average recruit is 26. She had been a nurse and medical assistant first, according to her profile on the career site LinkedIn. She was a mother of three.

Early Wednesday, Bonds was caught on video leaving a convenience store, then moving tightly along the wall, pulling a hoodie over his head and walking purposefully toward the command post vehicle with gloved hands, according to police. The video didn’t capture the shooting itself but showed him running away with a gun in his hand, police said.