Board Thread:Questions and Answers/@comment-28265951-20160421125919/@comment-3423279-20160601210613

Fairly certain that the fake Jay only existed during the scene in which he was killed.

And my definition of an alternate timeline is a timeline that is altered in some manner by time travel, the entire Arrowverse is an "alternate" timeline because of Eobard Thawne attacking the Allen family. Even a small change, like Barry going back in time one day to stop Mardon creates an alternate timeline.

The "Time Remnants" seem to be extremely percise use of this; a speedsters goes back about one second to exist with their past self, but since their "past" self now never goes and time travels the "current" world now it is an alternate timeline and they aren't connected to one another anymore and the future version can be killed.

Granted I don't recall if "Jay" was a future or past version of Hunter or not, but the Speed Force might ensure no time paradoxes if the past version is killed.

That is my interpretation of it anyways...