Bulugh al-Maram, Book 9, Hadith 1185 (In-Book)

Ibn ’Umar (RAA) narrated, ‘A young boy was murdered deceitfully. 'Umar (RAA) thereupon said, ‘If all the people of San'a’ (in Yemen) participated in killing him, I would kill them all.’ Related by al-Bukhari.

وَعَنْ اِبْنِ عُمَرَ رَضِيَ اَللَّهُ عَنْهُمَا قَالَ: { قُتِلَ غُلَامٌ غِيلَةً, فَقَالَ عُمَرُ: لَوْ اِشْتَرَكَ فِيهِ أَهْلُ صَنْعَاءَ لَقَتَلْتُهُمْ بِهِ }.‏ أَخْرَجَهُ اَلْبُخَارِيُّ 1‏ ‏1 ‏- صحيح.‏ رواه البخاري (6896)‏ وليس عنده لفظ: "به".‏

sunnah.com

also referenced under: Book 9, Hadith 1215 (English)