The Shot against Palme
The moment after the perpetrator had fired a shot against Olof Palme he shot again towards Lisbeth. The bullet grazed her back.
The former expert in profiling at FBI Robert Ressler claims that it was probably due to the intensity of the entire situation that the perpetrator “squeezed off” another shot against Lisbeth Palme. 
It is important to understand that a 100 per cent controlled shot is squeezed off whilst a rushed shot or a shot fired in panic is “pulled off”.
In the first incidence the weapons muzzle is not affected when it is handled by a professional shooter. In the second incidence the “pull off” forces the index finger to “pull” the weapon in such way that the muzzle moves rightwards. 
A random amateurs shot would never have grazed the back of Lisbeth Palme.
The substance abuser Christer Pettersson could have easily hit Olof Palme, because we are to believe that at the first shot the hammer on the revolver was cocked.
But since second shot occurs momentarily after the first shot the hammer is now being cocked by pulling the trigger, which at the same time makes the revolvers drum to spin. This action causes the muzzle to move rightwards when pulling the trigger and firing the shot. Skilled shooters know to turn their wrist left to hit the target. They “squeeze” another shot.
In other words: If the anything but revolver savvy Christer Pettersson fired the murder-weapon the second shot would have missed entirely. The recoil also known as knock-back would have caused the shot to be pulled up and towards right in relation to the target. The bullet would probably have hit a house in 3rd of 4th storage on the other side of Sveavägen.
Christer Andersson from the Academic Pistol Association (Akademiska PIstolklubben) was on the other hand a good at shooting in competitions. . He squeezed shots when he fired a revolver.
 Cf. Granskningskommissionen p. 906-907.
 Cf. Attorney (H) Niels Schou, former sharpshooter with pistol.
 Cf. Granskningskommissionen p. 958.