ALEXANDRIA — A federal grand jury has recently added new indictments to the 53-year-old Las Vegas man allegedly responsible for the kidnapping and death of 12-year-old Lexis Kaye Roberts, whose remains were found in the woods in Catahoula Parish in October.

According to a press release from the U.S. Department of Justice, Thomas Steven Sanders was indicted on charges of interstate kidnapping resulting in a death and use of a firearm in connection with a crime of violence.

The indictment alleges that between the days of Sept. 5 and Oct. 8, 2010, Sanders kidnapped Lexis in Arizona and then transported her to Louisiana, where he used a firearm to murder the girl.

Authorities say Sanders was in a relationship with Lexis’s mother, Suellen Roberts after meeting the woman in Las Vegas a few months prior.

Suellen and Lexis disappeared in Arizona after taking a road trip with Sanders over the Labor Day weekend, authorities said.

Lexis’s remains were found in the woods outside Harrisonburg Oct. 8.

Investigators believed her body was in that location for approximately a month before she was found.

Authorities say Lexis Roberts was shot by ammunition consistent with ammunition security cameras captured Sanders buying at a Walmart in Las Vegas on Sept. 3.

Sanders, who was legally pronounced dead in 1994 by family members, was arrested at a Gulfport truck stop at approximately 7 a.m. on Nov. 14.

Suellen’s body was found off Interstate 40 in Arizona in November, shortly after Sanders was taken into custody.

The Yavapai County Sheriff’s Office in Arizona and the Catahoula Parish Sheriff’s Office have said they suspect Sanders killed Suellen and her daughter.

According to the YCSO, Suellen’s death was classified as “undetermined homicidal violence,” and the autopsy revealed evidence of a gunshot wound to the head.

The U.S. Department of Justice office said Sanders will be arraigned on the new charges in front of U.S. magistrate Judge James Kirk and that an arraignment date has not been set.

Both counts of the indictment are punishable by either life in prison or death. The government does not know if it will seek a death penalty in the case as of now. According to Catahoula Parish District Attorney Brad Burget, in addition to the pending federal charges, Sanders also has a state detainer lodged against him on a warrant for first-degree-murder under Louisiana law.

The case is being investigated by the FBI, the CPSO, the Central Louisiana Safe Streets Task Force, the Las Vegas Metropolitan Police Department, the YCSO and the Coconino County Sheriff’s Office.

The federal indictment is being prosecuted by Assistant U.S. Attorneys William J. Flanagan and Nicole O. Snyder.