A 27-year-old Upper Marlboro man police have described as a serial killer was indicted Tuesday on two counts of first-degree murder.

A Prince George's County grand jury returned an indictment against Jason Thomas Scott in the deaths of Delores Dewitt, 42, and her 20-year-old daughter, Ebony. Their charred bodies were found in a burning car in Largo in March 2009.

In the seven-count indictment, Scott is also charged with two counts of burglary and three weapons offenses.

Glenn Ivey, the Prince George's County state's attorney, said there is an "ongoing investigation" into whether Scott is responsible for other slayings.

Scott is suspected of having killed another mother and daughter, 45-year-old Karen Lofton and 16-year-old Karissa, who were found shot to death in their Largo home in January 2009.

He is also a suspect in the 2008 death of Vilma Butler, a 47-year-old Bowie woman who was shot before her home was set on fire.

"We know that we have our killer" in all three of those incidents, Prince George's County Police Chief Roberto Hylton said.

Investigators are re-examining killings in Prince George's County and other areas to determine whether Scott is responsible for more slayings, Hylton said.

Neither Ivey nor Hylton would specify how Scott was linked to the Dewitt murders or other crimes.

Hylton only said investigators had "overwhelming evidence" in the Dewitt case and had found the "fruits of the various crimes he had committed" in Scott's home.

Scott is already in jail on federal weapons, child pornography and carjacking charges. Authorities began investigating him last year after the Bureau of Alcohol, Tobacco, Firearms and Explosives received a tip that he was selling firearms from the parking lot of his UPS job.

Ivey said Scott would not be eligible for the death penalty in the Dewitt killings, and prosecutors would instead seek life in prison without parole.

Under Maryland law, a killer can be sentenced to death only if there is DNA evidence, a videotaped confession or a video linking the suspect to the murder.

Ivey called the Dewitt case a "gruesome double murder that really shocked the community." Hylton said he hopes the indictment will result in more leads about other cases to which Scott might be connected.

"By no means do I think this investigation is over," he said.