BEDFORD COUNTY, Va. -- Investigators said they believe the case of two long-missing Maryland sisters is "closer to resolution than it's ever been" as they announced a new person of interest in the cold case Thursday, and said the case would go before a grand jury.
Sheila Lyon, 12, and her sister Katherine, 10, were last seen walking to the Wheaton Plaza mall in the Washington, D.C. suburb of Wheaton, Md., from their home in nearby Kensington in 1975. They were never seen again.
In February 2014, Montgomery County police and the FBI named a current Delaware inmate, Lloyd Lee Welch, Jr., as a person of interest in the case, reports CBS affiliate WUSA. They say Welch, Jr. was at the mall that day.
Thursday, Montgomery County police assistant chief Russ Hamill announced a second person of interest -- Richard Allen Welch Sr., believed to be Welch Jr.'s uncle.
Police believe Welch Sr. was a security guard in the Wheaton area when the girls disappeared. Hamill said he's still alive and police know where he is, though he wouldn't comment on his location.
Welch Sr. is also believed to own or have owned property on Taylor Mountain in Bedford County, Va., which has been the subject of searches in recent weeks. When asked whether he believes the girls are on the mountain, Hamill said, "I personally think there's a good chance."
The remote area between Roanoke and Lynchburg is more than 230 miles southwest of where the young sisters vanished.
The investigation is a joint effort between officials in Montgomery County, Maryland and Bedford, Virginia. A special grand jury is set to be impaneled Friday by the Bedford County Commonwealth's Attorney's office to begin hearing evidence and testimony in the case, Commonwealth's attorney Randy Krantz said.
The investigative grand jury has the ability to subpoena witnesses, documents and records, Krantz said.
Witnesses placed Lloyd Lee Welch, Jr. at the mall and said he was playing close attention to the girls, reports WUSA. In 1998, the 57-year-old Welch Jr. pleaded guilty to unrelated sex offenses in Delaware, where he is serving time, reports the Washington Post. He has reportedly denied any involvement in the sisters' disappearances.
Richard Allen Welch Sr., is believed to be over 70 years old. Hamill said that it's not clear whether he was a security guard at the mall or in the area. But he said there are those in both communities who may know what happened that day 39 years ago, and said it was their "moral responsibility" to contact police.
"We're asking people to come forward," Hamill said. "Now is the time for you to do the right thing, step forward and assist law enforcement to help us bring closure to this heart-wrenching matter."