It is narrated from Hazrat Abu Huraira (may Allah be pleased with him) in a marfu’ form that Allah Almighty laughs at two men, one of whom killed the other, but then both enter Paradise. The explanation is that one man was a disbeliever; he killed a Muslim, but before his own death, that disbeliever also accepted Islam, and Allah Almighty granted both of them entry into Paradise.
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 7326