Boston's police commissioner is reacting to the killing of two New York City police officers, apparently shot in retaliation for the death of Eric Garner.
"There's a lot of anger out there, there's a lot of frustration at police officers," said William Evans. "We can feel the tension out there."
The NYPD officers were gunned down as they sat in their car, raising troubling questions for cities like Boston, where protests have resulted in the wake of the Garner and Michael Brown cases.
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Mayor Marty Walsh says violence is not how people should express their frustrations.
"This is not the way to respond, by taking the life of two police officers, whose job is out there to protect the public," said Walsh.
To protect themselves, Boston Police are getting alerts to be more careful. For a time, two officers had been assigned to each cruiser, but that's not the case now.
They are not required to wear bullet-proof vests, although many do.
Three major protests have occurred in Boston, all of them were peaceful for the most part. But the city's police commissioner says the level of negative rhetoric directed at his officers - primarily, he says, from outsiders - was been disappointing, especially since 16 months ago, they were cheered for their handling of the attacks on the Boston Marathon.
"People take us for granted," said Evans. "When we're good, they love us, when something bad happens, they're very quick to throw us under the bus."