(Prince George’s Public Schools)

The armed intruder said nothing and took aim at no one else after shooting and killing 17-year-old Amber Stanley inside her bedroom at her family’s Kettering home, her mother said. Even when the intruder spotted Stanley’s half sister, he — or she — allowed the 37-year-old to grab her young son and flee through a window, the mother said.

On Friday, as friends and family members said their final goodbyes at a viewing in Landover, police returned to Stanley’s neighborhood to comb through sewer drains and woods for evidence in the case. More than a week after the slaying occurred, it remains just as mysterious to homicide detectives as to relatives.

“We don’t know who the person was after because my daughter’s lifestyle don’t warrant any kind of activity that would be suspect,” said Irma Gaither, Stanley’s mother. “That’s what’s so crazy about this.”

By all accounts, Stanley was a bright teenager who stayed out of trouble. A senior at Charles H. Flowers High School, she dreamed of studying genetics at Harvard University, friends and family said. In her free time, she worked as a model, impressing those much older than her with her mature runway walk and vivacious smile.

“When I saw her walk, I was like: ‘Wow. For a 17-year-old, this is really amazing,’ ” said Paul Cherry, 23, who modeled with Stanley and came to her viewing Friday. “I said, ‘This girl is going places.’ ”

Stanley was in her bedroom — probably organizing the school supplies that family members had bought that day — when the intruder came into her home on Chartsey Street just before 10:30 p.m. Aug. 22, Gaither and police said. Gaither had just run out to get a few more supplies, she said, but Stanley’s 37-year-old half sister and the woman’s 4-year-old son were home, along with a 17-year-old foster girl the family had been taking care of since January.

Gaither said Stanley’s half sister was doing laundry when she heard gunshots and ran upstairs. The half sister screamed as she saw the intruder back out of Stanley’s room but did not get a good look because she ran immediately to protect her son, Gaither said.

The half sister declined to talk to a reporter, and Gaither declined to identify her to protect her safety. Stanley’s half sister, her son and the foster girl eventually escaped out a window and ran to a neighbor’s house to call police, Gaither said.

Gaither said that the intruder did not speak to or fire at Stanley’s half sister. She said she wonders whether the attacker might have meant to target the foster girl, who has a troubled past and only the week before had reported to police that she was attacked while walking home from a store.

Law enforcement officials, speaking on the condition of anonymity because they could be disciplined for publicly discussing the ongoing investigation, said police are exploring that as one possible theory. The officials said police determined the girl’s attack report from the week before was “unfounded.”

Prince George’s Homicide Capt. Joseph Hoffman said detectives have been working on the case “nonstop” and hoped those with information might come forward.

“Somebody out there knows something,” Hoffman said. “We need to reach that person.”

Gaither said she has helped raised more than a dozen other foster kids over the years. For the most part, Gaither said, Stanley did not hang out with the girl. She said the foster girl has since been removed from her home.

Stanley, Gaither said, lived a somewhat “sheltered” life. She was just learning how to drive and on the night she was killed had considered going out to record some training hours, Gaither said. She enjoyed hosting movie nights for her girlfriends, picking up popcorn, cookies and sodas from Wegmans and turning her dad’s Upper Marlboro house into a theater, Gaither said.

And Stanley was learning — at her mom’s insistence — basic cooking skills, Gaither said. Gaither said that in the summer, she would make her daughter cook her oatmeal, eggs or English muffins every morning, in part to make sure Stanley ate a healthy breakfast. Stanley would also sometimes steam vegetables or shrimp for dinner, dousing them in alfredo sauce, Gaither said.

Gaither said she last saw her daughter on the night she was killed, when she told Stanley that the lip gloss she was wearing looked nice and asked her for a piece of gum.

At the viewing Friday, teary-eyed friends and family members streamed into Prince George’s Ballroom in Landover, hugging one another and sharing stories about Stanley, whose body was in an open, white casket, a wreath of pink and white flowers from her high school class by its side.

BillieJean Thompson, 28, who modeled with Stanley, said the teen had recently been selected to participate in D.C. Fashion Week, a significant honor for an aspiring model.

Yohanna Bradley, 50, who managed Stanley when she worked as a cashier at the Walter E. Washington Convention Center during the International AIDS Conference last month, said she was a “very sweet girl” who “had a smile all day.”

Michelle Steen, 40, Stanley’s cousin, said she was “just a beautiful child” who dreamed of becoming a doctor.

“It makes absolutely no sense, whatsoever,” Steen said of the slaying. “She had everything to live for.”

Magda Jean-Louis contributed to this report.