SEATTLE -- Three elderly brothers have been arrested in Seattle for allegedly possessing images of child sex abuse and other materials detectives say indicate the men spent the majority of their lives sexually abusing children.

The Seattle Times reports that 82-year-old Charles Emery, 80-year-old Thomas Emery and 78-year-old Edwin Emery were charged Monday with two counts of possession of depictions of minors engaged in sexual conduct. Law enforcement is "actively executing search warrants and interviewing witnesses to determine the extent of the defendants' child exploitation crimes as well as evidence of homicide," Senior Deputy Prosecutor Cecelia Gregson wrote in charging papers obtained by the Seattle Times.

Police say a family member was cleaning the men's North Seattle home and discovered what she believed to be materials depicting the sexual abuse of a child.

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The men's sister told CBS affiliate KIRO that it was her adult daughter who made the disturbing discovery Aug. 9. The daughter is reportedly the legal guardian of Charles Emery, who suffers from dementia and has moved into a residential care facility.

"She was in Charles' room. And I guess she was going through boxes and stuff to see what was in them. And she found these little [child's] shoes and stuff," the woman said.

She said her daughter immediately notified police.

"I still haven't gotten over the shock of it," the sister said.

Charging papers say authorities including members of the FBI's Internet Crimes Against Children Task Force searched the home for hours, finding evidence prosecutors say that each of the men exploited children depicted in child pornography. Detectives tell KIRO they discovered a massive amount of child pornography, along with children's worn clothing, underwear, small shoes, toys and movies. They also reportedly found a burned and partially buried girls' hat.

The brothers have lived in the home for 50 years and "have spent a lifetime accumulating" the cache of images and videos, the paper reports.

Capt. Mike Edwards of Seattle Police told KIRO investigators also found disturbing writings that "detail not only some of the sexual abuse and the interest in young female children, in addition to that, very graphic descriptions of harming and doing very disgusting things to children as well."

The discovery led investigators to dig under sheds at the home, the station reports. Charges say the handwritten notes detail the the "kidnapping, torturing, raping and murdering of young girls."

Charles Emery KIRO

"Their writings express desires to kill children," Edwards told the station. "It's very clear that these three individuals have an obsession with young female children, they've had this obsession for most if not all of their lives, and they acted on it."

Police tell KIRO they have evidence that indicates the Emerys sexually abused multiple young girls in their family decades ago. They say the victims are now adults. None of the brothers ever married or had children of their own, charges say.

Detectives aren't sure whether the brothers allegedly abused other children, but investigators around the area are watching the developments in the case closely for possible links to unsolved missing child cases.

The sheriff of nearby Grays Harbor County tells the station his department is particularly interested in a search planned for Saturday at a 17-acre property in Shelton, about 90 miles away, where another Emery brother, now deceased, lived until 2016.

Shelton is about a half hour away from McCleary, where 10-year-old Lindsey Baum vanished in 2009 walking back from a friend's house, one of the region's most highly publicized missing child cases.

"They would have had an opportunity to be in the McCleary area at the time of Lindsey's disappearance," the sheriff, Rick Scott, told KIRO. "They certainly would have been the type of people that would have victimized a girl her age."

A flier about Baum was found in the Shelton home, but there is no known connection between the brothers and the disappearance of Baum.

Cadaver dogs will aid in the search of the Shelton property Saturday, KIRO reports.

The three men have been jailed on $500,000 bail each.

The charges say Charles Emery was janitor at Seattle Children's Hospital from the 1970s through the 1990s. His sister confirmed that to KIRO, but the hospital says they can't confirm his employment there through their records. They said they are cooperating with prosecutors.