(Reuters) - A woman picking up her child at a Maryland high school was fatally shot on Thursday during a “domestic-related” altercation with a man who left the scene after also shooting a bystander who tried to intervene on the woman’s behalf, police said.

The Prince George’s County Police Department said the “domestic-related homicide” occurred after 4:30 p.m. (1330 PDT) at High Point High School in the community of Beltsville, Maryland, about 15 miles northeast of Washington.

Police Chief Henry Stawinski told an evening news conference that the deceased female and gunman “aren’t strangers to one another,” and that the injured man was shot after he tried to intervene in the fight between the woman and the gunman.

The suspect fired at the bystander, striking him once in the shoulder, and then turned the gun on the woman and shot her multiple times, killing her, Stawinski said. The bystander was expected to live, he said.

Police said they were actively looking for the male suspect after the shooting, which occurred after the normal school day had ended and students were heading to after-class activities.

Neither the victims nor the suspect were identified by police.

Kevin Maxwell, chief executive officer of Prince George’s County Public Schools, told reporters that no students were directly involved or harmed during the incident, though a number of them had witnessed portions of the shooting.

Other students, he said, were told to remain inside as the school was placed on lockdown.

Photos posted online by local media showed police and fire vehicles and officials in a crowded parking lot near the school’s auditorium.

A witness told local broadcaster FOX 5 that he heard four gunshots echo from the school’s back parking lot.