It is narrated from Sayyiduna Abu Hurayrah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "The killer cannot inherit."
Ishaq bin Abdullah is not used as evidence, but its supporting reports (shawahid) strengthen it, and Allah knows best.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الفرائض / 12243