Governor Deval Patrick is telling the residents of Boston, Watertown and 5 other neighbourhoods to stay inside.
The suburb of Watertown has a huge police presence with armoured vehicles and a swat team in one area.
A witness saw fresh blood in the area and police have been heard yelling at a building to come out.
Police are also conducting searches in the Cambridge area where the two suspects lived.
The two suspects are from Chechnya but have lived in the US since the early 2000's.
The older brother, a 26 year old, was killed in a gunfight overnight.
A 26 year old MIT police officer was killed in his car.
The search continues for 19 year old Dzhokhar Tsarnaev.
