He could have held back his anger. That is why he bore clear responsibility for his violent act.
فَقَايِينُ ،‏ بِكْرُ آدَمَ وَحَوَّاءَ ،‏ غَارَ مِنْ أَخِيهِ ٱلْأَصْغَرِ هَابِيلَ وَقَتَلَهُ مِنْ شِدَّةِ غَضَبِهِ .‏