Police said Friday morning at a Watertown news conference that one of the brothers stayed with the carjacking victim for a few minutes and then let him go.
They say one brother drove away in the CRV, and the other one drove away in the Mercedes.
Police say one then ditched the CRV and reunited with his brother in the Mercedes. Authorities say both suspects were in the Mercedes when they encountered police and hurled explosives at officers. Twenty-six-year-old suspect Tamerlan Tsarnaev was killed.
The CRV was later recovered in Boston.
Nineteen-year-old Dzhokhar Tsarnaev remains on the loose.