Depends if you are clearly outnumbered, for example 3 against 1 if you were to shoot the supposed robber then you would not be valuing your life. I would always recommend asking the person what will happen if you don't comply or whether they are threatening your life just to make sure.
Also to answer your question just shooting someone for saying "hands up" will definitely cause some issues in terms of breaking various rules like "Poor RP/RDM" so I would not recommend shooting someone at all after they say that after all you don't know their intentions and whether they are joking even if they are being serious.
@boomdark1