What caused the spatter pattern found on the west wall of the prime minister's outer office (where the deputy was found) ?

the cause of the blood spatter is arterial spurts

They managed to conclude this by identifying the type of drops that exist on the low. There are a lot of drops with relatively smaller in size, which indicates that the blood come out due to some sort of pressure that forced the blood out from small pipe in the body, like an arterial spurts