Sheila and Katherine Lyon disappeared in 1975.

Lloyd Welch pleaded guilty to two counts of murder yesterday in the killings of Katherine and Sheila Lyon, who vanished from a Maryland shopping mall 42 years ago.

The disappearance of the 10 and 12-year-olds left the Lyon family without answers for decades and shocked the community at large.

“That day in March was the day we lost our innocence,” John McCarthy, state’s attorney for Montgomery County, told reporters. “We began to rear our children differently. We began to think differently about what we could do. I guess there’s no way to turn that clock back, but the entire region was affected by this case.”

The sisters were visiting the Wheaton Plaza to shop for Easter decorations, but they never made it home. Police focused much of their search on a man with a tape recorder who had been seen talking to the girls. Welch, then an 18-year-old carnival worker, told a security guard a similar account that had been circulating in the press of the man, adding in details about an abduction. But when brought in for questioning, Welch failed a lie detector test and police dismissed him as an unreliable witness, according to the Washington Post.

In the intervening years, Welch pleaded guilty to several sex crimes. In 2013, the Montgomery County Police Department’s cold case division honed in on Welch, realizing that he matched the description of a man at the mall who had been seen staring at the sisters.

In 2014, he was named a person of interest in the case and he was charged in 2015 after a witness said he’d been seen burning two duffel bags that smelled like “death” a property that family members owned in Virginia.

Welch admitted he was a participant in the girls’ abduction, but did not admit to sexually assaulting or killing them. In interviews, Welch pinned their deaths on his father and uncle. His father has died, and prosecutors have said they don’t evidence to charge the uncle.

The 60-year-old Welch is serving time in Delaware until 2026 for sexually assaulting a 10-year-old girl, after which he will serve a 48-year sentence in the Lyon sisters case.