أَوْ قَتَلَهُ الْمُسْلِمُونَ ظُلْمًا وَلَمْ يَجِبْ بِقَتْلِهِ دِيَةٌ،
Translation: or one unjustly killed by Muslims where the killing does not give rise to an obligation of blood money (diyah),
The clause zulman denotes an unjust killing, and no diyah is due is a specific legal qualification.
Classical jurists distinguish cases whose primary legal remedy is retaliation (qisas) from those carrying compensation (diyah); this distinction affects the funeral classification described here.