Source: Tafsir al-Ahlam al-Kabir (Ibn Sirin)
Killing in a dream is a great sin. Whoever sees himself kill a person is committing a sin. Whoever sees himself killed will have a long life and receive goodness.
Source: Ta'tir al-Anam fi Ta'bir al-Manam (Al-Nabulsi)
Killing indicates salvation from worry. Whoever sees himself killed unjustly will gain high status and victory.
Source: Al-Isharat fi Ilm al-Ibarat (Ibn Shahin)
Killing is interpreted as goodness and benefit for the victim. Whoever sees himself kill himself has repented sincerely.