Rockville High School senior Michelle Miller was found dead in the Germantown home of a U.S. Army sergeant who helped recruit her. He shot Miller and then killed himself, according to Montgomery County police. (Courtesy of WJLA)

The man who shot a 17-year-old student and then killed himself in Montgomery County this week was a U.S. Army recruiter who worked at several local high schools and married a young former recruit last year, police said.

Police say Adam Arndt, 31, an Army staff sergeant, shot Michelle Miller, a Rockville High School senior, before killing himself Monday in his Germantown home, where both bodies were found later that day. Michelle was an honor student and a new recruit who was set to begin basic training this summer, according to her father.

Family and friends continued to mourn her death Tuesday, attending an evening memorial vigil at Rockville High School. Buddha Ratna, a family friend, said Michelle’s mother was taken to a hospital after fainting. An ambulance and a firetruck arrived at the school as the memorial was wrapping up.

Meanwhile, a portrait began to emerge of a married man who was romantically involved with one teenager and sending text messages and Facebook notes to others.

Friends of Michelle’s have told law enforcement officials that the two were romantically linked, according to officials who spoke on the condition of anonymity because the investigation is ongoing. Arndt was married to a 21-year-old Army recruit, Kaitlyn, who enlisted at the same Gaithersburg recruiting center where Arndt worked and is currently posted in North Carolina.

Michelle Miller (Courtesy of Rockville High School)

Kaitlyn Arndt declined to be interviewed when reached by telephone Tuesday, but friends and local students said she and Arndt were engaged and married within a few weeks’ time last year. The wedding took place in June with both families present.

“They seemed to be a great couple,” said Kaitlyn’s mother, Paula Schum, who recalled that the two had been talking about starting a family. “It seemed like such a whirlwind. It’s just such a shock and such a horrible thing.”

Neither of Kaitlyn Arndt’s parents had heard or suspected anything about Arndt’s involvement with Miller. “I’m in total disbelief,” said her father, Randy, who had seen his son-in-law only a handful of times since the wedding. “This is unbelievable.”

Neither Kaitlyn’s father nor Army officials knew how the two first met or whether Arndt had recruited her. Denise Coates, a friend of Adam Arndt, said that the marriage seemed to be going well but that “the one challenge was distance.” The couple alternated weekend visits to Maryland and North Carolina. His previous marriage had ended badly, but he seemed happy about his new life, Coates said.

A decorated soldier from Manitowoc, Wis., who won the Army Commendation Medal three times, Adam Arndt began working as an Army recruiter in January 2011 after returning from posts in South Korea, Germany, Turkey and Fort Benning, Ga., according to Army spokeswoman Kathleen Welker. In addition to his recruiting work, Arndt also led a mentoring program at Poolesville High School, said Dana Tofig, a spokesman for Montgomery County schools.

Arndt had also worked previously as a “future soldier leader” — a mentor for new recruits headed to basic training. Michelle had been an enthusiastic future soldier, said Brian Lepley, a spokesman for the Army Recruiting Command. Arndt would have interacted with her at training sessions, he said.

Rockville High School’s principal, Debra Munk, said she did not know how Miller and Arndt first met or whether Arndt had an official role as a recruiter at the school. Tofig, the schools spokesman, said that “recruiters generally will set up a table during lunch period or at some other time. They may not wander the halls unaccompanied.

Federal law mandates that schools give military recruiters the same access to students that colleges and universities receive, Tofig said.

Parents and students who knew of Arndt through his recruiting work said his relationships with some students, including text messages and notes through Facebook, made them uncomfortable.

Army recruiters are prohibited from socializing with recruits before they enter basic training, said Lepley, the Army recruiting spokesman. Recruiters cannot be alone with recruits, are forbidden to make personal phone calls or send text messages to them, and may use Facebook only for official purposes, he said.

The Army has yet to decide whether the case will prompt an evaluation of recruiting practices.“The only thing the Army can do at this point, because there is an investigation, is express that the battalion is deeply saddened by the loss of Staff Sgt. Adam Arndt and Michelle Miller,” said Army spokesman Mark Rickert, speaking Tuesday outside the Gaithersburg recruiting center, where young men and women were walking in for an afternoon session.

Lynh Bui and Dan Morse contributed to this report.