In a desolate corner of the Bronx, Ana Charle ran a shelter for homeless men with mental illness. Many of them came to see her as an anchor in their otherwise turbulent lives.

But one man apparently saw her through very different eyes.

West Spruill left the Bronx Boulevard Men’s Shelter at the beginning of the year, only to return about four months later to stalk Ms. Charle, according to the police. On Monday night, he waited outside the shelter, clutching two bags containing a gun and plastic wrist ties. He had a scrap of paper with the license plate number of her car parked around the corner.

He grabbed Ms. Charle and forced her to get into the car and undress while he did the same, the police said. Ms. Charle, 36, got free and fled naked as he chased after her. He raised his gun and fatally shot her at close range, in the temple, cheek and chest. She fell to the sidewalk.

Her killing left some of the men at the shelter in tears. Some became more distraught when they learned that the suspect was someone they had slept beside, shared meals with and trusted with their confidences.