Jaelynn Willey, 16, is in life-threatening condition with critical injuries after being shot at Great Mills High School in Maryland on Tuesday. (YouCaring)

A 16-year-old girl who was critically injured in a shooting at a Maryland high school earlier this week has died, police said.

The St. Mary's County Sheriff's Office announced Friday that Jaelynn Willey died Thursday at 11:34 p.m. ET while surrounded by family.

Willey's parents announced earlier Thursday night that their daugther was brain dead and would be taken off life support at University of Maryland Prince George's Hospital Center.

Melissa Willey told reporters that her daughter, Jaelynn, has "no life left in her."

"On Tuesday ... our lives changed completely and totally forever," Melissa Willey said. "My daughter was hurt by a boy who shot her in the head and took everything from our lives."

Willey was shot by 17-year-old Austin Rollins at Great Mills High School. (File)

Jaelynn Willey was shot in the head by 17-year-old Austin Rollins at Great Mills High School. Investigators said that Willey and Rollins had recently ended a relationship and the shooting was not random.

Rollins was fatally shot after being confronted by an armed school resource officer, thought it is not clear whether Rollins took his own life or was killed by the officer.

An error occurred while retrieving the Tweet. It might have been deleted.

Willey had been in critical condition at the University of Maryland Prince George's Hospital Center. A fundraising page to help her family has raised more than $78,000.

Jaelynn was one of nine siblings, her mother said, and a member of the swim team.

A 14-year-old boy who was shot in the thigh during the encounter was released Wednesday from a hospital.

In an email Thursday to The Associated Press, his mother, Kimberly Dennis, said her family is "eternally grateful" that her son, Desmond Barnes, is "alive, doing well and in good spirits."

She expressed sympathy for Willey and her family and added, "We are also praying for the entire Great Mills High School family and young people around this country. As a community and nation, we must continue to work and fight for a world that is safe for our children."

Great Mills High School has about 1,600 students and is near the Patuxent River Naval Air Station, about 65 miles southeast of Washington.

St. Mary's County Sheriff Tim Cameron credited Deputy First Class Blaine Gaskill with preventing any more loss of life.

Cameron said Gaskill, a six-year veteran with SWAT team training, responded within a minute and fired his weapon simultaneously with a final shot fired by Rollins. The officer was unharmed.

On Wednesday, authorities said the Glock handgun used in the shooting was legally owned by Rollins' father. In Maryland it is illegal for anyone under age 21 to possess a handgun unless it is required for their employment.

The Associated Press contributed to this report.