A 45-year-old woman was fatally shot while standing behind her closed apartment door on Sunday, and police sources say she may have been targeted because her son is on trial for a 2014 murder.

Police say Wendy Martinez was shot in her face in her apartment in the Concourse Village section of the Bronx. Officers responded to a call about the shooting at 9:42 p.m. and EMS pronounced her dead at the scene.

A neighbor told CBS 2, "It was no argument. It was just one shot—pow—and then footsteps running."

According to the Post's sources, she had gone to the door when the doorbell rang: "Martinez asked who it was but got no reply, according to sources. She asked again after a second ring, and then slid open the peephole when she heard no response. That’s when the gunman pumped a single, fatal shot through the viewing slot that struck Martinez’s face." The sources added that there's surveillance video of the shooter but an umbrella was shielding his face.

Her 14-year-old son, who was in the apartment at the time, called 911.

Martinez's 25-year-old son Brian Solano was arrested in 2014 for the murder of Willie Lora. He spent three years on Rikers awaiting trial, but was released on his own recognizance late last year after a private investigator determined that two grand jury witnesses said their testimony was coerced by police. Solano, who maintains he is innocent, had a court hearing in the murder case scheduled for today, the Post reports.

Manuel Gomez, the private investigator who helped uncover the evidence, believes that Martinez was killed as retribution for Lora's murder. In an interview with WABC 7, he said that her family has been "receiving death treats for more than two years—documented in court. DA was aware as well, but nothing was done—no protective measures taken to protect this family." He also called Martinez "an innocent lady. Good woman who was loved by the community."

The Daily News notes, "Gomez’s tactics have been called into question. He was recently accused by a Queens judge of coercing a witness of a gang slaying into not testifying."