The 21-year-old Washington state woman arrested for allegedly shooting and killing a U.S. Customs and Border Protection agent earlier this week had cellphones wrapped in foil and a stash of tactical gear and ammunition in her car when reportedly she fired at the agent during a traffic stop in Vermont near the U.S.-Canada border, authorities said.
Teresa Youngblut, 21, allegedly shot Border Patrol officer David Maland during a traffic stop on Monday along Interstate 91 in Coventry. The incident took place while Youngblut was traveling with a friend, Felix Baukholt, according to the FBI. Maland pulled over Youngblut and Baukholt, a German national, because Baukholt's visa appeared to be expired.
Murderer Duo

Youngblut was behind the wheel of a blue Toyota Prius, while Baukholt, whose visa had expired, was in the passenger seat, according to a newly unsealed affidavit obtained by NBC affiliate WPTZ. At the time of the stop, agents on the scene reported that both Youngblut and Baukholt had guns.
As agents approached the vehicle, Youngblut allegedly fired two shots at them, while Baukholt tried to snatch one of their guns, authorities said.

Maland was hit, and the agents returned fire, fatally shooting Baukholt and wounding Youngblut in the process.
Youngblut was transported to a nearby hospital, where she is still receiving treatment. Maland was also rushed to the hospital but was pronounced dead within the hour.
After clearing the scene, investigators found a cache of disturbing items hidden inside the Prius, including a Washington state ID belonging to Youngblut, according to police.

Other than the two guns and ammunition magazines, cops also found cell phones wrapped in aluminum foil and several laptops. When the FBI arrived, they discovered tactical equipment, such as a ballistic helmet, a night vision monocular, a tactical belt, and hollow-point ammunition.
A journal belonging to Youngblut was found in the car, along with a package of shooting range targets and two handheld two-way radios, according to the affidavit.
Moving with an Arsenal
The couple had been under surveillance since January 14, when a hotel worker in Lyndonville, another town in Vermont, noticed them dressed in tactical gear and carrying firearms. When officers approached them that day, the pair, both wearing N-95 masks, told the police they were in the area to look at real estate.

On January 19, they were spotted again in nearby Newport, still wearing the same gear, with Youngblut seen carrying a gun once again.
Surveillance footage showed them purchasing foil at a Walmart and wrapping it around an item in the parking lot just before the shooting.
Baulkholt was a skilled computer expert who won college math competitions for his celebrated research, sources told the Vermont Daily Chronicle. His identity was revealed in a report by the Toronto Sun.
He had worked for a major international finance firm in New York City until last year, using his expertise to bet against the stock market, according to a former classmate.
At one point, Baulkholt was reportedly living and working in the U.S. on an O-1A visa, which is granted to individuals with "extraordinary ability in the sciences, education, business, or athletics."
His most recent position was as a quantitative trader with Tower Research Capital, according to an online profile. In this role, he used complex mathematical models and algorithms to analyze the stock market and help investors in making informed predictions.
Baulkholt attended the University of Waterloo in Ontario, where he was part of their demanding computer science and math program.