1 If he is an heir and he killed someone he will inherit from, then his punishment is that he will be cut out of the inheritance.
2 The atonement for the killer is that he is killed unless the family and guardians of the victim forgive the killer and accept blood money. If he is forgiven then he should give an expatiation.
(And whoever kills a believer intentionally, their reward will be Hell—where they will stay indefinitely.1 Allah will be displeased with them, condemn them, and will prepare for them a tremendous punishment.) An-Nisa’a 4: 92
أولا : الحرمان من الميراث إذا قتل وريث.
ثانيا: القصاص من القاتل بقتله، إلا اذا عفا اولياء المقتول او رضوا بالدية، فاذا عفي عن القاتل وجب عليه الكفارة، قال الله تعالى
(وَمَن يَقْتُلْ مُؤْمِنًا مُّتَعَمِّدًا فَجَزَاؤُهُ جَهَنَّمُ خَالِدًا فِيهَا وَغَضِبَ اللَّهُ عَلَيْهِ وَلَعَنَهُ وَأَعَدَّ لَهُ عَذَابًا عَظِيمًا ﴿ النساء 4 :93.