Of course, but if you get the jump and shoot, then you won't be able to use the Death from Above anymore, as that attack uses the same buttons as the shooting. Unless they make the death from above a weapon you only equip when you have selected your fists in the weapons wheel.
I wonder why Volition didn't think of that. When you have no weapon equiped, you can do the normal Death from Above attack. When you have a melee weapon, you use that weapon with the Death from Above (except the stun gun of course) and when you have a normal weapon, you can not do the Death from Above, but you can shoot.
Please, Volition! If you read this, put it on the table as a future patch or DLC! (Not gonna happen probably, as you need to alter significant files, and it wouldn't be fair for the colsole players.)