Agreed with the others, and I'll also point out that of all the Fallen, Thorned Namshiel appears to be the most laid back of the thirty. He can destroy you or have a cup of tea with equal preference, he doesn't seem to hold grudges very deeply, and based on our few interactions with him he likes the direct approach to payback.
Even if it wasn't a coincidence and there was Fallen influence in Murphey's death, I find it extremely unlikely that Namshiel's hand would have been behind it.