Metro police issued a "be on the lookout" warning for the second Boston bombing suspect early Friday evening.Dzhokhar Tsarnaev may be driving a green 1999 Honda Accord with Massachusetts license plate number 166GC7. Tsarnaev and his brother twenty-six-year-old Tamerlan is suspected of killing a Massachusetts Institute of Technology police officer late Thursday, then stealing a car at gunpoint.The suspects' clashes with police began hours after the FBI released photos and videos of them. Monday's bombings killed three people and wounded more than 180 others.Tamerlan Tsarnaev was killed overnight. His 19-year-old brother, Dzhokhar remains on the loose.*The Associated Press contributed to this report.