A woman was shot and killed and a man was seriously wounded in Charles County on Friday night as they walked near a high school, authorities said.

The shooting occurred about 7 p.m. as the two were walking a dog on a path that leads from Hampshire Circle toward Westlake High School in the Waldorf area of the county, Charles County sheriff’s officials said.

The motive in the shooting remained unclear on Saturday, the sheriff’s office said. As they walked, with the dog on a leash, the man and woman passed someone who opened fire for “unknown reasons,” the sheriff’s office said in a news release.

The man’s age was given as 43, and the woman’s as 40. Neither was identified.

School system officials said there was no indication that either of the victims was connected to the school.

The shooting “did not involve the school,” said Katherine O’Malley-Simpson, the chief spokeswoman for the school system.

However, it was apparently close enough to Westlake to be heard by sheriff’s deputies who were nearby to provide security at a football game at the school Friday night.

Diane Richardson, a spokeswoman for the sheriff’s office, called the shooting a highly unusual event in a normally quiet neighborhood.

A helicopter landed near the school to take at least one of the victims to a hospital, O’Malley-Simpson said.