A jury has found Lee Malvo (18) guilty of murdering Linda Franklin, one of 10 people gunned down in a series of sniper shootings that terrorised the Washington, DC, area last year.
Malvo was 17 when he and his accomplice John Muhammad (42) roamed the region in an old car, picking off random people by shooting through a hole cut in the car's boot. However, he was tried as an adult and now faces the death penalty or life in prison without parole.
Malvo sat without apparent reaction as a court official read out guilty verdicts in each of two counts of capital murder.
"We are extremely pleased with the verdict," said Mr Bob Meyers, the brother of another of the pair's victims, Dean Meyers, who was shot on October 9th, 2002, at a petrol station near Manassas, Virginia.
A separate jury last month convicted Muhammad of Mr Meyers's murder and sentenced the Gulf War veteran to death. A judge will review the recommendation and make a final sentencing in February.
Malvo was found guilty of killing Ms Franklin and of participating in the murder of Mr Meyers. In the second count, Malvo was found guilty of killing Ms Franklin as an act of terrorism. The jury also found him guilty on a third count of using a firearm in commission of a felony, a verdict that carries an automatic three-year sentence.