The book’s second proper name is ʿUthmān.
جَاءَ عُثْمَانُ — ʿUthmān came: nominative subject with ḍamma.
رَأَيْتُ عُثْمَانَ — I saw ʿUthmān: accusative object with fatḥa.
سَلَّمْتُ عَلَى عُثْمَانَ — I greeted ʿUthmān: genitive after ʿalā, marked by fatḥa.