Shooting Mr Connally With Standard Assumptions

An M91/38 carbine does 5d pi.  That is 5-30 points of damage (17.5 average) with ball ammo to the body.

The second shot hits Kennedy in the back, exits the front and hits Connally in the back, exits the front and hits his wrist (hand location for GURPS).

Using the standard Overpenetration rules on page B408, a person provides a DR of what ever DR they're wearing on each side penetrated and their hit points.

So a person wearing DR 3 front and back with a ST of 12 will provide DR 18 for the person standing behind them; or in front if them if shot in the back.

Kennedy is not wearing armor, and we're assuming his frail condition leaves him 10 hit points; so he's DR 10 for Connally.

Connally's torso is DR 10 to protect his wrist.

So, as before; 23 points of damage will penetrate both Kennedy and Connally's torsos and do enough damage to cripple the hand and cause Connally to drop his hat.

The difference is Kennedy takes 23 points of damage to the torso this time.  Then Connally takes 13 to the torso and then 3 to the hand.

So Kennedy will need a consciousness roll (which he makes because he's holding his throat when round number 3 hits him in the skull) and will need a death roll (which he also appears to make).  The 60 that we assigned to the skull brings him to -73 hit points.  -50 is auto death.

Connally needs two consciousness rolls (he makes both) and will not need a death roll because he's only at -6 HP.

The Kennedy Assassination still GURPS.

Update:  Alternate rules interpretation:

One could take the position that you roll the 5d pi damage for every thing in the path of the bullet and subtract the DR of the intervening cover each time.

So Kennedy just needs to take more than HP worth of damage to allow the round to hit Connally and then Connally has to take more than HP worth of damage to get to the hand and that just needs 3 points to cripple it, and 5 is the minimum.