What a murder must not be, in order to avoid a trail of secondary effects like a murder charge or a murder sentence, was down to four points:
it mustnít be slow: victim was not to react in any way or the thing would have complicated very, very fast;
inaccurate: see above;
noisy: for plain reasons;
and it mustnít be performed at short range; a priority avoiding traces on you, such as blood splashes, gunpowder, wounds by the victim.
And, of course, no partners. One killer, one secret.
All that wasnít slow, inaccurate, noisy, short ranged, and could be performed by one man formed the option pool to choose from. More unwelcome secondary effects, like a murder enquiry, were harder to avoid. They were part of the wall most killer wannabesí plans ended up smashed on. Everyone wanted no-one to notice. Everyone wanted it to look like an accident, and
messed up their lives.