BLOOMING GROVE, Pa. - The words, police said, read like the diary of a calculated killer:

"Fri. Sept. 12th, got a shot around 11 pm and took it. . . . He droped.[sic] . . . I was surprised at how quick. I took a follow-up shot on his head/neck area. . . . He was still and quiet after."

The quote came from a journal state police said Eric Frein wrote after ambushing two troopers last month, unleashing the most massive manhunt in years in Northeastern Pennsylvania.

In their first substantive update in days, investigators announced new charges, and released new photos and details about the 31-year-old gunman who has eluded them for weeks. They said they had no doubt Frein remains hidden in the same dense forest in Monroe and Pike Counties that they have been scouring - and that they have found sites he abandoned and evidence to suggest that his supplies may be dwindling.

The search has already cost several million dollars, but the handwritten pages - recovered last week at a campsite - were a reminder of why authorities need to devote all the resources they can to catch Frein, Lt. Col. George Bivens said.

"I will tell you, after reading this cold-blooded and absolutely chilling account, I can only describe Eric Frein's actions as pure evil," Bivens told reporters at a Wednesday afternoon news conference.

A self-styled survivalist from Canadensis, Frein is charged in the shooting death of State Police Cpl. Bryon Dickson and the attempted murder of Trooper Alex Douglass. Both were ambushed Sept. 12 outside the state police's Blooming Grove barracks.

Police have said Frein planned such an attack and retreat for years - they found a book on sniper training in his bedroom. Documents they filed in connection with the investigation also show that Frein allegedly searched the Internet in 2012 and 2013 for information on police raids, cellphone tracking, and manhunt tactics.

The journal they say they recovered seemed to offer the strongest evidence to date of Frein's premeditation. Neither it nor investigators have said why he targeted the barracks, although they said the writings suggest that Frein did not know the troopers he attacked.

In it, Frein described shooting the second trooper as the officer knelt to help the first.

Frein wrote that he ran back to his Jeep and drove away, according to journal excerpts cited in a criminal affidavit. He turned into a nearby neighborhood to avoid a police roadblock, but then turned off his headlights because he heard helicopters above, the document said.

Then Frein's Jeep got stuck in the mud. "!Disaster!" is written.

Still, Frein has since eluded more than 1,000 troopers, federal agents, and others combing hundreds of acres of Poconos woods. He has been spotted four times by police or residents since Friday, Bivens said.

The woods are so dense in some areas that officers tracking him cannot see each other from 10 or 15 feet away, Bivens said, and must sling their rifles over their shoulders to crawl through the underbrush. Frein, who knows the woods well and studied how to hide from police, disappears before search teams can identify him or reach him, Bivens said.

"So it's not as simple as being on an open football field, for example, and seeing someone 75 or 100 yards away," he said.

Authorities added charges against Frein on Wednesday, for possession of two weapons of mass destruction. Investigators discovered two pipe bombs last week, and found powders and other bomb-making materials in Frein's bedroom at his parents' house.

Sam Rabadi, the head of the Philadelphia division of the Bureau of Alcohol, Tobacco, Firearms and Explosives, said the explosives were fully functional, and included shrapnel and booby traps that could have been set to seriously injure anyone who stumbled upon them.

Bivens said he remains certain Frein is in a roughly five-square-mile area on the border of Monroe and Pike Counties. Search teams found a large rocky ledge with nooks that they believe Frein used to hide and build small campfires, Bivens said, and other areas where they believe he has slept.

The fugitive likely still has supplies and food stashed in some areas, Bivens said, though he believes Frein will run out of supplies. When he is spotted by residents or police, Bivens said, Frein is often not carrying anything, as if he is scouting out a new area.

Based on descriptions of his appearance and clothing, police are fairly certain the sightings have been Frein.

But, Bivens said, "the only way we know it's a positive sighting is [when] we have him in custody."

On Wednesday, officers carrying rifles and using dogs appeared to walk the same wooded areas they have searched for weeks.

Barrett Township, where signs remind visitors that hunting season is on hold and residents attempt to continue their daily routines, was largely quiet. Neighbors swapped stories of the search, and shop owners complained that business remains slow during what should be the busy fall season.

Authorities apologized for the strain the search has placed on residents, but stressed that Frein is a danger to the public.

The FBI, which has added Frein to its Ten Most Wanted list, is also devoting resources to the search. Jeffrey Walker, assistant special agent in charge of the Philadelphia division of the FBI, unveiled new images on Wednesday of Frein with facial hair and a mohawk haircut.

"The manpower and resources that have been committed here are exactly what any community in these circumstances would hope it to be," said Pike County District Attorney Ray Tonkin. "Ultimately it will be this approach that will bring Eric Frein to face justice."