The invention refers to an auto injector (1) and to a method for operating it the auto injector comprising: a tubular chassis (2) a carrier subassembly comprising a tubular carrier (7) slidably arranged in the chassis (2) the carrier (7) containing a syringe (3) with a hollow injection needle (4) a drive spring (8) and a plunger (9) for forwarding load of the drive spring (8) to a stopper (6) of the syringe (3) a wrap over trigger sleeve (12) arranged over the distal end (D) of the auto injector (1) the trigger sleeve (12) extending at least almost over the whole length of the auto injector (1) a control spring (19) arranged around the carrier (7) first interlock means (20 22 23 24) for coupling a proximal end of the control spring (19) to either the carrier (7) for advancing it for needle insertion or to the chassis (2) for needle retraction second interlock means (11 13 15) arranged for releasing the drive spring (8) for injection third interlock means (16 17 18) arranged for coupling the chassis (2) to the carrier (7) for joint axial translation relative to the trigger sleeve (12) fourth interlock means (21 25 26 28) arranged for coupling a distal end of the control spring (19) to either the carrier (7) for needle retraction or to the trigger sleeve (12) otherwise.
