Boston police are asking for media not to reveal the positions of the officers as they are doing the house-to-house search. But I'm sitting here, listening on my cellphone to them talking on their radios...
As to the use of lethal force, these are heavily armed suspects, likely wearing suicide vests, who have alreade engaged police in a heavy exchange of fire. While I hope no more lives are lost, in my judgement lethal force can be used if needed, i.e. if he is found and can't be stopped by other means. If an angry drunk stands in his yard with a shotgun and won't follow police orders, then you should try a shot to the leg but this may be a step beyond that.
Legshots are by no means a "safe" method for incapacitating a subject without killing them. It's very easy, moreso in the legs than say, the arms(though it's probable even with an arm shot), to rupture a major artery. Shooting the kneecap will most likely cripple the person for life, which is especially bad in the case they are innocent of what the police are after them for and their actions are the result of fear of arrest - and don't say they wouldn't run if they weren't innocent, if a
cop anyone draws a gun and starts shouting at you, fight-or-flight
will kick in overdrive - or in the case of a shotgun drunk, extreme consequence for what is probably a misdemeanor(assuming the weapon is not discharged).
There's a reason tazers exist, and even though those aren't neccessarily non-lethal, they're a lot safer than a gun in incapacitating someone.
That said, I believe deadly force is appropriate for this situation. There was probable reason to believe the suspects were highly dangerous in the first place, and they
did fire on police, resulting in at least one police fatality, from what I heard.