A man suspected in the notorious disappearance and murder of the Lyon sisters plans to plead guilty in the case, a source confirmed to WUSA9 reporter Bruce Leshan.

Lloyd Welch Jr. was scheduled to go on trial for murder this year in the deaths of 12-year-old Sheila Lyon and 10-year-old Katherine Lyon. The sisters were walking about one-half mile from the Wheaton Plaza Mall to their home in Kensington when they disappeared.

Their bodies were never found.

Welch was charged with two counts of murder in 2015. Authorities say Welch, a former carnival worker, was at the mall the day the girls vanished and was seen paying attention to them.

Welch was identified as a suspect in 2013. He had been in a Delaware prison since 1997, when he was convicted of sexually assaulting a 10-year-old girl in the 90s. He's a twice convicted child sex offender.

The Lyon sisters case shook the D.C. suburb and changed how people in the community lived.

"It was very scary at the time," recalled Jane Harding, who lives around the corner from the Lyons. Harding has lived there since the 1950s.

She said police did not initially think the girls were abducted.

"They were being treated as runaways so it wasn't as serious, we thought, as children who were being abducted," said Harding.

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But soon everything would change. Police changed their approach from runaways to abductees and the community changed the way they lived.

"Everyone was afraid to let their children outside to play because these two young girls had just disappeared," said Harding. "It was like having your own child disappear."