Harold smith was a very complex character, so it does not seem so unusal that he committed suicide. He had some psychological issues, and as a result nobody questions his suicide. But what if Harold never committed suicide? What if he was murdered?

In Fire Walk With Me (FWWM), Laura pays a visit to Harold and confides in him. She tells him that BOB does not know about him. The Log Lady mentions that she is safe from the owls in her cabin. In other wordas the owls (vessels for BOB to possess) can not see what goes on in the cabin. Similarly, Harolds house is a sanctuary from BOB, as he cannot see what goes on in there, nor who lives in it... hence, Harold is a secret from BOB.

So, Harold's phobia of the outdoors is not necessarily a bad thing. If Harold was to expose himself to the outdoors then he would no longer be a secret from BOB. And this is indeed what happens when he chases Donna Hayward out of his house, only to falter. This is the turning point of Harold's life. All of a sudden he is exposed to the prying eyes of the owls, and BOB knows all about him. BOB, after seeing Harold, kills him.

The prying eyes of the owls are not the only means for BOB to learn of Harold's existence. The psychological impact of his stepping outside generated a great deal of fear. BOB is drawn to fear, we learn this when he is drawn to Josie when she dies of fright!

So, we have two logical arguments which suggest that Harold Smith was killed by BOB. Add this to the facts that he swore he would kill again, and that BOB had not finished spelling out his name under people's fingernails, and the pieces gradually begin to fall intoplace. But what would they have discovered if they had looked under poor Harold's fingernail...?