WASHINGTON (AP) — Boston's police commissioner says investigators believe the suspects in the marathon bombing were likely planning other attacks.

Commissioner Ed Davis told CBS' "Face the Nation" on Sunday that authorities found an arsenal of homemade explosives following a gun battle between police and the suspects last week in Watertown, Mass.

Davis says authorities have reason to believe 19-year-old Dzhokhar Tsarnaev and 26-year-old brother Tamerlan "were going to attack other individuals."

He says the scene of the gun battle was "loaded with unexploded improvised explosive devices that actually we had to point out to the arriving officers and clear the area."

He said on "Fox News Sunday" authorities cannot be positive there aren't more explosives that haven't been found. But he says the people of Boston are safe.

Meantime, the Massachusetts State Police Air Wing has released video from a helicopter showing a robotic arm tearing away covering from the boat in which Dzhokhar Tsarnaev was hiding. The video also shows the "flash-bang" grenades deployed to disorientate Tsarnaev.

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