A 20-year-old American named Kevin Dahlgren accused of the grisly murders of his uncle, aunt and two cousins in the Czech Republic was arrested Thursday night at Washington's Dulles International Airport, the FBI's Washington field office confirmed to ABC News.
The Czech regional police chief in the city of Brno had issued an international arrest warrant for Dahlgren, and he is being held on a provisional arrest warrant at the request of Czech officials, ABC News has learned.
A federal complaint filed Thursday in U.S. District Court for Eastern Virginia said Dahlgren had killed his relatives at their home Tuesday or Wednesday, stabbing the victims in the head and neck, The Associated Press reported.
Dahlgren appeared Friday morning in U.S. District Court in Alexandria and was ordered detained pending a status hearing Wednesday, reported the AP.
U.S. prosecutors are trying to keep Dahlgren in the Unied States until he can be returned to face charges in the Czech Republic, which has 60 days to ask for his extradition, reported the AP.
Czech police had targeted Dahlgren and circulated a picture from his Facebook account to police stations, border posts, immigration counters and media outlets across the country. Authorities in neighboring countries had reportedly been alerted to detain Dahlgren, whose Facebook description says he is from Palo Alto, Calif.
Neighbors said Dahlgren had been visiting his aunt and uncle, Veronika and Martin Harok, and their two sons, 22-year-old Filip and 18-year-old David, in Brno. They were all found dead by firefighters who responded to what they believe was an attempt by the alleged killer to cover up the crimes.
"We were originally called to intervene against a fire. On the spot the suspicions arose that a violent crime had been committed. We immediately called the police," firefighters' spokesman Jaroslav Mikoska told ABC News.
Veronika Harok was a Czech language teacher at the local elementary school. Martin Harok and his son Filip were musicians who played several nights a week with a local ukulele orchestra, while the youngest victim, David Harok, was described as very involved in sports.
Bozena Zikuskova, a local restaurant owner, told ABC News that Dahlgren would come every other day and always order the same meal. She noted that Dahlgren's Czech was not even good enough to order a meal.
Karel Herman, the front man of Ukulele Orchestra Jako Brno band in which Martin and Flilp Harok played, said "Dahlgren was just visiting his cousins. He arrived in early May and was a completely normal guy."
Neighbors said the crime had shocked the community.
"It's not something you expect from the neighborhood," said , Jan Kral, 56, who said he had lived in the area for 30 years. His wife, Paulina, agreed. "It's frightening," she said. "Very frightening."
ABC News' Luis Martinez, Jack Cloherty, Karin Halperin and The Associated Press contributed to this report.