Speaker 1: New developments in the deadly shooting of a Border Patrol agent in Vermont. The agent shot and killed during a traffic stop near the Canadian border. One suspect was killed in the shootout. A second suspect wounded and now facing charges. Court records showing authorities had them under surveillance nearly a week before the shooting. Here's ABC's chief justice correspondent, Pierre Thomas.

Speaker 2: Tonight, a Washington state woman is facing charges in the first killing of a Border Patrol agent in more than a decade. Authorities say 21-year-old Teresa Youngblood and Felix Bockholt, a German citizen on an expired visa, engaged police in a hail of gunfire along Interstate 91 in Coventry, Vermont, about 20 miles from the Canadian border. 44-year-old Border Patrol agent David Chris Maland died later at a local hospital.

Speaker 3: I want to extend my heartfelt condolences to Agent Maland's family, friends and colleagues.

Speaker 2: According to a federal affidavit, investigators had been conducting periodic surveillance of the pair for more than a week after an employee at a nearby hotel reported them checking in dressed in all black tactical style clothing, with Youngblood carrying an apparent firearm and an exposed carry holster. When authorities made contact, they say the pair told them they were in the vicinity to look at purchasing property. Bockholt was killed, Youngblood wounded. Inside the vehicle, police say they found a cache of weapons, body armor and two-way radios. Tonight, this case is a mystery. Why did that traffic stop end in such a violent confrontation? Witt?

Speaker 1: Still a lot of questions. Pierre Thomas, thank you.