Katherine Lyon, 10 and Sheila Lyon, 12, from Kennsington, Md., were last seen walking to the Wheaton Plaza mall in 1975.

Authorities on Wednesday announced first-degree murder charges against an imprisoned sex offender in the disappearance of two sisters from a suburban Maryland mall in 1975, bringing some clarity to the baffling case that made parents question whether to allow children out of their homes alone.

Katherine Lyon, left, and Sheila Lyon, right, went to see an Easter exhibit and grab a slice of pizza from the mall on March 25, 1975 and have been missing ever since. Neither man has been charged.

Welch’s uncle, 70-year-old Richard Welch, had also been named a person of interest in the case.

Since past year, authorities have been searching a mountain in Bedford County, Va., about 200 miles from Wheaton, for their remains.

“If you have anyone in Montgomery County, they can tell you a personal story about how they or their family was impacted”, said Montgomery County Police Chief J.

Randy Krantz, the commonwealth’s attorney in Bedford County, said Welch could face 20 years to life in prison if he is convicted. Montgomery County State’s Attorney John McCarthy said they “did not choose to be victims” and “beg you for their privacy”.

As the case progressed, investigators revealed in a court affidavit that Lloyd Welch admitted leaving the shopping center in a auto that day with the girls, his uncle, Richard Welch, and a juvenile.

They were supposed to come home by 4 p.m. When they didn’t, their mother called authorities and a major search ensued, according to the Charley Project, a website that profiles thousands of missing people, mainly from the United States.

Maryland police previous year identified Welch, who is serving time in the Vaughn Correctional Center near Smyrna, Del., as a “person of interest” in the cold case. During a press conference in Wheaton, Maryland, where the girls disappeared, law enforcement announced charges against Welch. Welch says he never saw the girls again.

According to police affidavits obtained by The Post, Lloyd Welch told investigators that he left the mall with the two girls and that he saw his uncle sexually assaulting one of them at his home the next day. The abuse that led to his current prison term began shortly after Welch started watching a pornographic video while a girl “was in the living room area with him”, according to court records.

Soon after the girls disappeared, Welch allegedly arrived at his cousin’s property carrying a duffel bag of bloody clothes, the Post reported.

Manger said his officers have “never given up on finding these girls”.

For the past two years, investigators have been looking at Welch, but the grand jury proceedings in Bedford County, where Welch relatives have owned land, have been closed to the public.

Officials stressed Wednesday that the investigation remains active.