What does the affirmative imperfect “yabkī” do in «جَاءَ الْوَلَدُ يَبْكِي»?

Supplementary Practice 2: Editing Rhetorical Expression, Context and Reasoning

• Answers an oath
• Describes the concurrent state of arrival without a circumstantial wāw
• Makes the past verb passive
• Necessarily asserts an unrelated independent event