An indicator appears, which points to other players.

I have seen this three times. Once it pointed at a player, once another player saw one pointing at me, and another time it pointed at a car. It is possible it points at some object being carried or contained, rather than at the player/car per se.

The indicator looks like two triangles, which appear on walls and floors, tinted slightly darker than the rest of the texture. Sometimes the triangles are easy to see, and other times difficult, depending on how flat and plain the surface is.

The indicator is very responsive to movement of the target. The range is at least 200 meters.