Probably they are good. Nobody can deny that they have a good reason to locate the fugitive. They probably have a warrant that says "Search for this guy anywhere within Boston and suburbs" - and that warrant is good enough at this time. (Nobody can be expected to do better.)
What records are they keeping? This guy had a gun? This guy had drug paraphenalia on his coffee table?
That shouldn't be a concern for two reasons.
Legally, they are searching for a specific man. This warrant says nothing about searching premises for drugs or firearms. The plain view doctrine still may be used, however, because the visit by the LEO would be otherwise lawful.
But practically, they cannot stop and arrest people for minor violations. The police doesn't have enough resources as they are to search the whole city. Just imagine what would the police commanders be screaming into their radios if their officers start wasting their time citing people for $100 warrants or for a gram or two of pot while the mass murderer is making his escape. I don't think SWAT teams are even set up to run subjects and to do investigations on the spot. It's a job of a beat cop.