Manhattan District Attorney Alvin L. Bragg Jr. said in a statement that Isaac Argro killed Johnson, the mother of their 3-month-old child, "in a premeditated act of fatal domestic violence."
“Committing this type of killing in front of an infant is horrific, and I cannot imagine the pain that Ms. Johnson’s family and loved ones are experiencing," Bragg added. "I want to make clear that we will pursue full accountability and justice in this case.”
Johnson and Argro had planned to meet up on June 29 to exchange items for their daughter. But authorities said Argro, dressed in black with a ski mask over his face, shot Johnson in the head and then fled the scene, discarding the clothes he was wearing.
After he fled, Argro called Johnson's family to ask where his child was and threatened someone else, telling them they were "next," according to the prosecutor's office.
Johnson was pronounced dead at the hospital and the infant survived.
Argro was charged with murder in the second degree and criminal possession of a weapon.
Lisa Desort, Johnson's mother, previously told NBC New York that Johnson was a victim of domestic abuse during one of her pregnancies.
"The city failed my daughter because on January 1, my daughter called me and said she was being abused while she was six months pregnant," Desort told the station. "She was scared to call the police so she gave me the address. I called police."
Earlier this month, Desort told the New York Post that Argro was an angry person and at one point, Johnson was so worried about his behavior that she fled to a domestic violence shelter.