The "midst" of something in the Bible represents the thing that is most central and most important to the spiritual state being described, the motivation that drives everything else. In general this will be something we love or feel, because at the core of things we are what we love; our loves define us.

(References: Apocalypse Revealed 44, 90, 268; Arcana Coelestia 2252, 2940, 10153, 10365, 10557, 10635, 10641)

10365. 'That soul will be cut off from the midst of his people' means that not heaven and the Church but hell resides with that person. This is clear from the meaning of 'being cut off from the midst of his people' as separation from the Church and spiritual death, dealt with in 10288, so that not the Church but hell resides with him. When the Church does not reside with a person, neither does heaven; for heaven and the Church act as one. In the case of a person in whom the Church is present heaven, that is, the Lord by way of heaven, flows in and constitutes the Church there. So it is that when the Church does not reside with a person hell does so; and this is therefore meant by 'being cut off from the midst of his people'.