SPOTSYLVANIA, Va. - The teenager arrested in the sniper slayings may have fired the shot that killed an FBI analyst, a prosecutor said Monday as Virginia charged both suspects with crimes that could bring the death penalty.

John Lee Malvo, 17, and John Allen Muhammad, 41, now face murder charges in both Virginia and Maryland in the three-week series of attacks that killed 10 people and wounded three. Alabama has charged them in a killing during a robbery. No decision had been made yet on federal charges.

Fairfax County prosecutor Robert Horan Jr. said evidence shows that Malvo may have fired the shot that killed Linda Franklin on Oct. 14 outside a Home Depot in Falls Church. He would not elaborate on the evidence.

"There will be some evidence that the juvenile was the shooter just like there will be evidence that the adult was the shooter," Horan said. "But the point is, we don't know right now, and no one knows right now."

The pair were charged in Spotsylvania County with the murder of Kenneth Bridges on Oct. 11 and the Oct. 4 wounding of an unidentified woman. The murder charges were based on state law allowing capital punishment for the killing of more than one person within three years.

In Prince William County, where Dean Meyers was slain Oct. 9 while pumping gas, a grand jury charged Muhammad and Malvo with capital murder and conspiracy to commit murder under a new post-Sept. 11 terrorism law.

Prince William prosecutor Paul Ebert said that law would allow the death penalty for both men - even the man who did not pull the trigger.

Virginia Attorney General Jerry W. Kilgore said the terrorism law gives Virginia prosecutors a "backup, another option in their arsenal" to seek the death penalty against Muhammad or Malvo if either eludes a death sentence for capital murder.

That boosts the case for allowing Virginia to try the suspects promptly, if not first, Kilgore said.

"The terrorism law includes not only the shooter but the masterminds behind these acts," Kilgore said. "We feel very confident that what these individuals have done fits within the definition of terrorism in this law."

In Hanover County, where an unidentified man was wounded on Oct. 19, the two suspects were also named in a variety of charges including attempted murder and terrorizing the public.

In all three Virginia counties, the charges against Malvo were made in juvenile court, but authorities said they would seek to have his case transferred to adult court.

County, state and federal prosecutors have yet to figure out who will bring the two men to trial first.

Spotsylvania County Sheriff Ronald Knight said Muhammad and Malvo should be tried in Virginia as soon as possible. "Everybody is looking for that to happen since Virginia has the death penalty" for both adults and juveniles, the sheriff said.

In Maryland, 17-year-olds are not eligible for the death penalty. There is no death penalty in the District of Columbia, where one person was killed.

Virginia, which allows condemned prisoners to choose between lethal injection and the electric chair, has executed 86 people since capital punishment was reinstated in 1976, more than any other state except Texas. In the same period, Maryland has executed three people and is one of two states with a moratorium on executions.

Over the weekend, Montgomery County, Md., prosecutor Douglas Gansler said he believes his state should prosecute the men first, in part because Maryland had the most slayings: six.

Kilgore said if Maryland prosecutes first, "then we will wait our turn and take our turn. We hope that decision is made sooner rather than later."

A senior Justice Department official, speaking on condition of anonymity, said discussions continued Monday on whether the federal government would bring its own charges. The overriding concern, the official said, is to ensure that a swift, certain death penalty is available if either defendant is convicted.

(Associated Press writers Curt Anderson, Matt Barakat, Justin Bergman and Bob Lewis contributed to this story.)