Helgoth mayhave been part of it -- very plausible scenario on your part.
However, he also could have committed suicide just as you describe it. Follow:
Hold a pillow to your left side/Chest, Reach across with your right hand as if holding a gun, simulate a shot.
Your right hand is not braced, as such when the gun is fired the bullet will enter right where you aim (Peircing your heart or vital organs - either way you have killed yourself successfully) -- now the recoil of the gun is unimpeded as your right hand/arm is not braced as it would on a normal shot -- The gun will recoil straight at the angle you are holding it, with your right hand across your body it will fly back and right, you have just shot yourself in the chest, your body will go straight back, you will open your grip from the shock to your body
At this point physics take over. You right arm will land either across your abdomen or fly to the right side of your body, the gun which is now heading back and to your right and no longer held will land at your RIGHT SIDE most likely between your shoulder and hip.
This is wildly improbable. If I shot myself on the left side with my right hand (who would even think to do this? It's really awkward), the pistol would drop to my left side, and my arm, most likely, would land across my torso, not on the right side.
I have pretty long arms (35" sleeve), but I don't think I could do this with a pillow. The gun was a Glock, which means the shooter's hand would have to have been about 5 inches back from the body, plus another 3 or so to account for the pillow. The angle of the bullet was such that the shot entered really from the left side, not at an angle; about perpendicular to the front of the body. I just can't envision this being a suicide.