One of the last times Hannah Graham was seen, it was early Saturday, Sept. 13, and a camera outside a gas station in Charlottesville, Virginia, briefly filmed her walking, then running. A few minutes before, Graham, a second-year student at the University of Virginia, was seen talking to a man outside McGrady’s Pub, a bar not far from campus; shortly after 1 a.m., she sent a text message to a friend: she was lost. Then, the eighteen-year-old vanished.

In the days after, Graham's disappearance has rattled the small Virginia community, leaving residents, friends and family to wonder — What happened to Hannah? Here’s what we know so far.

Who is Hannah Graham?

Graham went to high school in Northern Virginia, at West Potomac. Relatives and people who knew Graham described her as a resilient and responsible young woman — a thoughtful student who liked to ski, loved Starburst candy and played the alto saxophone. Graham “was very diligent with everything she did, and always did everything exactly by the book,” as Stephen Rice, a band director at West Potomac, put it in an interview with NBC Washington. “Hannah is not the kind of kid that would just go on a road trip and disappear.”

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Graham is 5-foot-11; she has blue eyes, light brown hair and freckles, and on Saturday night, she was wearing black pants and a crop top. Before disappearing, she had attended an off-campus party.

Who is the person of interest?

At a news conference on Sunday, Charlottesville Police Chief Timothy Longo said that he believed Jesse Matthew, 32, was the last person Graham “was seen with before she vanished off the face of the earth.” Matthew is believed to appear in surveillance video walking with Graham; police searched his car and apartment and are awaiting forensic results. Matthew has not been charged in Graham’s disappearance, and on Saturday, he arrived at Charlottesville police headquarters, asked for a lawyer, and then left without speaking to police. A warrant was later issued for his arrest on charges of reckless driving.

At the news conference, Longo pleaded for Matthew’s cooperation. “I hope and pray that we might have an opportunity to talk to Jesse Matthew again,” Longo said. “We want to talk to him about his interaction with a sweet young girl that we can’t find.”

How has the community responded?

Graham is one of five girls to go missing in the Charlottesville area in the last five years, and for some, her disappearance has been a "debilitating" process, as Gil Harrington, whose daughter, Morgan, was among them, put it. Morgan was later found dead. Amanda St.Clair created a Facebook page this week for Graham. "There's a problem here," St.Clair told NBC News. "They just disappeared into thin air."

On Thursday, an estimated 2,000 people gathered at a candlelight vigil at the university. Some brought mementos — a pair of skis, an alto saxophone — others wished her safe return.

University president Teresa A. Sullivan released a statement Sunday saying the school is helping authorities in the search for Graham. "We are cooperating fully with law enforcement authorities as they continue their investigation. If you have any information that might be helpful, no matter how inconsequential it might seem to you, please call the dedicated tip line at 434-295-3851."

What’s next?

"This investigation has been aggressive and will continue to be aggressive," police chief Tim Longo said at a press conference Wednesday, and over the weekend, more than 1,000 people turned out to search for Graham; so many volunteers arrived at John Paul Jones Arena on Friday that they needed to be arranged in groups and assigned different start times. Though it covered 85 percent of the city, Graham was not found. Still, the search coordinator, Mark Eggeman, said Sunday that the effort “generated more leads,” and that in the days ahead it would become more narrowly focused.

At a Sunday news conference, Graham’s father, John Graham, thanked the volunteers for their “marvelous support,” but he pleaded for more help. “Who saw Hannah?” he said. “Somebody knows what happened to Hannah.”