Visible crew/equipment: As K opens the door to the Cosmic Bowl bowling alley, the camera crew and equipment is reflected in it.
Visible crew/equipment: After J arrives in 1969 and stands on the sidewalk at the Empire State Building, look at the doors behind him. As they close and open, the lighting rigs are reflected.
Chosen answer: He saw J's father murdered by Boris. In the unaltered timeline, J says that his father wasn't around. We see this at the end and it's also why J was recruited into the Men In Black. K was keeping an eye on him the whole time.
Brad ★