On further investigation, this is a completely bogus story. Police reenacted the shootout scene using the actual vehicles; the 1999 green Honda Civic that Dzhokar had access to, and the carjacked black Merecedes SUV. The story does not indicate investigators are in doubt about where the vehicles came from.
Both cars were at the shoot out, pictures were taken by a resident in house . Honda had the Coexist sticker. Speculation is brothers were loading items from Honda into SUV
You gotta give the crack reporters at NBC a little more credit. They just figured out that the brothers drove TWO cars to the shoot out. At least they finally figured it out. Maybe they'll soon realize that these guys might be terrorists.