You could make an argument that you should wear a Level IIa jacket too... But people usually don't.
We also don't know how the husband was shot. Was he shot from behind? Was the shooter concealed?
As has been said - having a gun doesn't protect you from a sniper. If it did - snipers wouldn't be even 1/10th as effective as they are because 99% of their targets are armed.
However, body armor probably would have protected Ralph Aldrich, aside from a head shot, a jacket with front and back Level IIa panels would have stopped an arrow.
I don't know how the situation unfolded with June Aldrich, but probably a case could be made that having a gun would have helped her.