The mother of a 1-month-old boy who died in a fall from a Queens apartment building has been charged with murder, police said Saturday.

Rashida Chowdhury, 21, was arrested on charges of second-degree murder and intentional murder of a person under 11 years old, after the city medical examiner's office ruled the child's death a homicide, according to the NYPD.

The infant, Rizwan Ahmad, was found dead in the courtyard of the building at 85-55 115th St. in Richmond Hill about 4 a.m. Friday, police said.

He died of blunt impact injuries to his head and torso after plunging from a fourth-floor window, police said.

Mazol Ilyayeva, a resident of the building who saw the deceased baby in the courtyard, said Saturday that she is struggling to understand what transpired before Rizwan's death.

"I want to know what happened," she said. "I don't understand how a 21-year-old mother can turn against her own child and throw him out a window as if he were trash."

It was not immediately clear whether Chowdhury had an attorney. She is expected to be arraigned Saturday in Queens Criminal Court.