My understanding is that the Younis killing could have been a result of tribal rivalries. It could have been revenge for something Younis did while a Gaddafi general.. It could have been financed by Gaddafi.   Or other possible factors.   Or a combination of the above.

Point is:   the perpetrators should be caught and punished. And the entire Gaddafi opposition should return to the business at hand:   removing Gaddafi from power.