in time your pain of losing your friend will not be as intense. but you will always look back to the times you shared together. i know. i lost my best friend this way. R.I.P. maryjane. i was out of town on business but wondered if i had been there if things would not turn out as they did. we lived within walking distance to each other.
as for feeling guilty there is no way of stopping the intention. you are not at fault. ppl who do what tom did have planned it for some time, sam. also he was entangled with addiction. addiction takes many lives and leaves their loved ones in limbo. so many "what ifs" for us even if their death was unintended.
i hope you will consider this. there is no reason for you to feel responsible.
i'm so glad you posted. it helps to talk about our experiences that trouble us.