1)
4) Massachusetts has some strange rules about a citizen's arrest. Basically, it does not recognize a privilege for a citizen to arrest for a misdemeanor and it does not recognize a citizen's use of deadly force to effect any arrest.
IANAL, but this from the Self Defense Jury Instructions (
http://www.northeastshooters.com/vb...ions?highlight=self+defense+jury+instructions):
A person may use deadly
force to make a citizen’s arrest only if:
First, he (she) believes that such force is necessary to
make a lawful arrest;
Second, the arrest is for a felony;
Third, either he (she) announces the purpose of the arrest
or believes it is already known to the person being arrested or
believes it cannot reasonably be made known to the person
being arrested;
Fourth, either he (she) is assisting a person whom he (she)
believes is a peace officer; or he (she) is a peace officer;
Fifth, he (she) believes there is no substantial risk of injury
to innocent persons;
Sixth, he (she) believes that the person being arrested
used or threatened to use force in committing the felony;
Seventh, he (she) believes that there is a substantial risk
that the person being arrested will cause death or serious bodily
harm to someone if he (she) is not immediately arrested.
The fifth paragraph is the stickiest, though. Again, IANAL. Could you argue that you called 911 and were assisting the unamed policeman who was going to arrive.