All observers see the same Speed of Light, so all observers must see spherical wave fronts from a point source of light, regardless of their velocities.
So
Cases
and the two events can be conencted only by a light signal. The events are said to have a light-like separation and so no signal can travel fast enough to connect the two events. The events are not causally connected and are said to have space-like separation and so the two events can be causally connect. The interval is said to be time-like