A portion of the police report reviewed by the Wall Street Journal suggests an answer: Because the driver wasn’t American, at least in the eyes of the two suspects:
The victim told police he was driven to a Shell Gas Station on Memorial Drive in Watertown. Inside the car, the brothers “declared to [the victim] that they were the Boston Marathon bombers and would not kill him because he wasn’t American,” the report said. When the victim saw an opportunity to flee, he ran to a nearby gas station where he asked the owner to call 911, the report said.
The unnamed victim spoke with NBC News this morning and confirmed the story, while also describing Dzhokhar and Tamerlan Tsarnaev as “brutal and cautious.” The brothers allegedly stole the victim’s Mercedes SUV at gunpoint late Thursday, less than an hour after they allegedly shot and killed a MIT police officer in Cambridge. According to the police report, one of the brothers—it hasn’t been specified which one—got into the SUV at about 11 p.m. in Boston’s Brighton neighborhood, and at gunpoint ordered the man to drive him to Watertown. He was followed by the other brother in a second car, a Honda Civic, according to police. According to the victim, at some point while in Watertown he saw his chance to flee and ran to a nearby gas station where he asked the owner to call 911.