“When one Muslim wields his weapon against his brother, both of them are at the edge of Hell, and if one of them kills the other, they will both enter it.” (Using translation from Ibn Mājah 3965)
"إذا الْتقى المسلمانِ حَمَلَ أحدهما على أخيه السلاح فهما على حرفِ جهنّمَ فإذا قَتَلَ أحدُهما صاحبَه دَخَلاها جميعًا" .