Police say, Yong Kim, 57, opened fire on his wife, stepdaughter and two young children, then killed himself, at this home on Amberleigh Drive, in the Colesville area of Montgomery County, Md. The lone survivor, the 22-year-old stepdaughter, is in critical condition at a hospital. (Dan Morse/The Washington Post)

A 11-year-old girl gravely wounded during a shooting rampage by her father in their Montgomery County home has died, bringing to four the family members killed by Yong Mun Kim, police officials said Friday.

The death of Mina Kim on Thursday leaves one shooting survivor: a 22-year-old who remains hospitalized. Her condition has improved from critical to stable, said Sgt. Rebecca Innocenti, a Montgomery police spokeswoman.

Several days ago — at 12:06 a.m. Monday — the 22-year-old called 911 to the home on Amberleigh Drive, in the Colesville area about 10 miles north of the District, according to police officials. They say the woman’s stepfather, Yong Kim, 57, opened fire on his wife, Sang Yeon Kim, 48, the 22-year-old, and his two young children, Mina, 11, and Andy, 10. Then, police say, Kim used his revolver to kill himself.

Kim and his wife died at the scene. Andy, Mina and the 22-year-old were taken to hospitals. Andy, a fourth grader at Westover Elementary School, died shortly after arriving, according to police and school officials. Mina’s condition never improved, Innocenti said.

The 10-year-old and the 11-year-old were the children of Yong Kim and Sang Kim, according to Innocenti. The 22-year-old is the daughter of Sang Kim from a previous relationship, she said.

Police have said that Yong Kim’s relationship with Sang Kim had become strained.

The back of the Kim family’s house. (Dan Morse/The Washington Post)

On the night of the shootings, it appears Sang Kim was sleeping in her 22-year-old daughter’s bedroom. The youngest child, Andy, also had gone to sleep in the same room.

“That was not an unusual sleeping arrangement,” Innocenti said.

Detectives theorized that Yong Kim was staying in a different room and they continue to sort out exactly what prompted him to erupt in such violence, and they may never know, Innocenti said.

“All of that is still under investigation,” Innocenti said.

Police have classified the deaths of the children and Sang Kim as homicides. They classified Yong Kim’s death as a suicide.

In earlier interviews, several people who knew Yong Kim from years past described him as cheerful and friendly.

“This guy would never say a bad word. You would never see him mad,” said Rami Kouncar, his boss for six years at an auto-repair shop in White Oak.

The Greene family, who lived next door to him until recently, said he would fix their cars free, bring them Asian pears every Christmas, and could often be heard singing from inside his house.

“I can’t come to grips with this,” said Shannon Greene, 21, a college student. “It’s just horrible.”