The sister of the survivalist suspected of killing a Pennsylvania trooper and wounding another three weeks ago said on Saturday she thought her brother had fled the area, and she urged him to surrender to authorities.

Tiffany Frein, the 18-year-old sister of Eric Frein, said she believed an intensive manhunt, involving hundreds of officers, has failed to capture her brother because he was not in the deep woods of the Pocono Mountains where they have been searching.

"I think if he were here they definitely would have found him by now," she said, while walking her German shepherd on a dirt road by her family's home in Canadensis, Pennsylvania.

If she could talk to her brother, Tiffany Frein told a reporter, she would tell him "to do us all a favor and turn yourself in."

Troopers carrying assault weapons were out in full force again Saturday not far from the house where Eric Frein had lived until a few weeks before a sniper shot and killed Corporal Bryon Dickson, 38, and critically wounding Trooper Alex Douglass, 31, on Sept. 12.

"This is too much," the sister said. "This is just too stressful."

Officers have also reported spotting Frein, 31, in the woods, just out of reach, on several occasions during the manhunt, though not in recent days.

Earlier this week police said that a search team came across a campsite that contained clothing, food and ammunition believed to have belonged to the suspect, an expert marksman who is now on the FBI's Most Wanted List.

With the discovery of the cache, authorities are more convinced than ever that Frein is hiding in a five-square-mile area in the northeastern corner of the state, taking refuge in the state forests and game lands that blanket the region.

She said she would ask her brother, who she said was a straight-A student in school, one question: "Why?"

The sister said police told the family that Eric had tried to call their home but it went unanswered, she said, because no one was home at the time.

Tiffany Frein, a student at a community college, said Eric was a "good brother," and had no idea what could have caused him to do what the police claim he did on Sept. 12.

She said her parents are not taking it well. "It's hard," she said. "They don't talk about it."