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CHICAGO — Chicago police are looking for a man who forced his way into an apartment and killed a mother of three in the Ravenswood Manor neighborhood.

Police said 27-year-old Stephanie Brooks was with a male friend inside a second-floor apartment on the 4400 block of North Francisco Avenue around 9:30 p.m. Monday. There was a knock on the door and when the friend opened it, a man dressed in all black — and wearing a ski mask — tried forcing his way inside.

Brooks was shot in the chest by the intruder as she tried to close the door, according to police. She was pronounced dead at the scene. The friend was not injured.

Police said this shooting was targeted and an act of retaliation in connection to the Feb. 2 shooting of a Chicago firefighter. The firefighter was working to put out a car fire in the 3600 block of West Wilson in Albany Park, when he became caught in the crossfire of a gang-related shooting.

Police told WGN one of the several men arrested that night was charged with gun possession. One of those men is believed to have been associated with Brooks.

Police also told WGN they are anticipating a very high-level of retaliation from the murder of Brooks. Authorities are now devoting their gang resources to the 17th Police District to see how they can curb this anticipated violence.

Chicago police said these shootings also relate back to a drug house on Wilson Avenue, which is near where the firefighter was shot.

No one is in custody as Area North detectives investigate.