(AP) - A Mount Rainier National Park ranger was fatally shot Sunday following a routine traffic stop, and authorities closed the 368-square-mile park in Washington state as they searched for the armed gunman, a park spokeswoman said. She had set up a vehicle as a roadblock on a park road just before the shooting, which happened at about 11 a.m. near the Longmire Ranger Station in the southwestern part of the park, Lee Taylor said. Ed Troyer, a Pierce County Sheriff's spokesman, said his department received a report around 11:30 a.m. of shots fired in the park and a ranger in need of help. When authorities arrived, Troyer said, they also encountered gunfire, but no one else was hit. Authorities removed Anderson from the park and found that she was dead, Troyer said. Authorities believe the gunman is still in the woods with an assault rifle. They are asking people to stay away from the park, and for those already inside the park to leave. Authorities were stopping and questioning people as they departed. Troyer said his department has received reports of cars with bullet holes. He did not have further details and said communication was limited because there is no cellphone service in the park. Park superintendent Randy King said that Anderson is a mother of two young daughters who has served as a park ranger for about four years. King said Anderson's husband also was working as a ranger elsewhere in the park at the time of the shooting. "It's just a huge tragedy - for the family, the park and the park service," he said. The shooting occurred on an unseasonably sunny and mild New Year's Day. The park, which offers miles of wooded trails and spectacular vistas from which to see 14,410-foot Mount Rainier, draws between 1.5 million and 2 million visitors each year. The Longmire station served as headquarters when the national park was established in 1899. The Washington State Patrol also was helping with the investigation.