All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
If you had read the full text of this Hadeeth, you would have found the answer to your question. The Companions asked the Prophet the same question as they said: “It is alright for the murderer, but what about the murdered one?” Thereupon, the Prophet said: “He was keen (i.e. had the intention) to kill his companion.” This is evidence that determination, which is having a strong intention and willingness to absolutely do something, makes the person liable to the punishment for the intended act, even if he did not actually do it. That is because the killed person was keen and willing to kill his fellow Muslim was it not that the first (his fellow Muslim) killed him. An-Nawawi when interpreting this Hadeeth, said: “This is evidence of the correct view of the majority of the scholars that if a person intends to commit a sin, and he was firm in his intention, then he is sinful, even if he did not actually do it and did not speak about it.”
Allaah Knows best.