Sherlock Holmes Riddle

I say it’s… Actually, I won’t say. I haven’t look at the answer yet in an effort to draw out the suspense for myself. Here it is for you. 

And yay! I’m right. Although I don’t know why people have to murder each other in these brain teasers. One of them is about a family of four where someone gets murdered, someone helps and someone is a witness. Nice.