The northeastern Pennsylvania high school once attended by the suspect in a deadly police ambush -- and subject of a five-week manhunt -- was on heightened security Monday after a woman reported seeing him nearby. 

A woman out for a walk Friday night spotted the man near Pocono Mountain East High School shortly after 9 p.m., state police said. Investigators said the man was about 15 to 20 feet from the woman, just off the road where she was walking in Swiftwater. He was holding a rifle and his face was smeared with mud, the woman told police. Authorities believe the man was Eric Frein, an expert marksman and survivalist who has eluded capture despite an intense manhunt in the Pocono Mountains 

The Pocono Mountain School District said the high school and all other district schools are open Monday. Additional police officers and security officials are on hand to protect students.

"Frein is familiar with this area, as he had attended Pocono Mountain East High School, worked briefly at Sanolfi Pasteur and also worked several summers at Camp Minsi," Lt. Col. George Bivens said Saturday, according to local media reports.

"The individual's description was consistent with Frein, and he was observed carrying a rifle," Bivens said. "The individual's face was covered with mud, so a positive identification could not be made. A search of the area is ongoing."

Frein, 31, is charged with opening fire Sept. 12 outside the rural Blooming Grove state police barracks, killing Cpl. Bryon Dickson and seriously injuring Trooper Alex Douglass in an unprovoked attack. Additional charges have also been filed following the discovery of explosives allegedly set by Frein.

Authorities had said they have Frein contained in a 5-mile radius. On Sept. 18, six days after the deadly ambush, Frein tried to call his parents' home from his cellphone, which was tracked to Monroe County.

Police found traces of Frein since he slipped into the vast wilderness of the Poconos following the deadly ambush. The items include diapers, a discarded rifle, ammunition and several pipe bombs believed to be planted by Frein.  

Authorities said they also found a "chilling" journal in the woods, in which Frein allegedly described shooting the state troopers.

"Got a shot around 11 p.m. and took it," Frein wrote on papers found by police. "He [Dickson] dropped. I was surprised at how quick."

The Associated Press contributed to this report.