He was stabbed with a poisonous blade whilst leading a prayer, according to some in the head, by a non-mulsim assassin named Abu-Lu'lua. Abu Lu'lua had a grudge against Umar because Umar, supposedly, made a ruling against him, and Abu Lu'lua thought it was unjust. Umar later died due to the wound, and he was buried in next to the prophet Muhammad (SAW).
Umar ibn Hafsun died in 918.
Yahya ibn Umar died in 864.
Sayf ibn Umar died in 796.
Ali ibn Umar died in 883.
Yahya ibn Idris ibn Umar died in 917.
Abu Bakr, Umar ibn al-Khattab, Uthman ibn Affan, and Ali ibn Abi Talib.
The 2nd Caliph Umar Ibn Al-Khattab.
You need to be more specific about which Umar are you talking about. Umar is an Islamic name. If you are referring to one of the notable Muslim Caliph Umar, his father was Khattab Ibn Nufayl.
Umar Ibn Muhammad of Borno died in 1967.
Abû 'Umar ibn Sa'îd died in 1287.
Al-Qadi Aqib ibn Mahmud ibn Umar died in 1627.
Yahya ibn Umar al-Lamtuni died in 1056.