Is it possible to trigger the flash mid-photo?

Hi all

I was wondering, is it possible to make the flash trigger while the shutter is opened? Let's assume a 3 second shutter speed. You have a person walk in front of the camera. I want my flash to trigger after 1.5 seconds of pressing the shutter button so I can freeze the person mid frame, but the camera can capture his body moving through the hole frame to create some kind of shadow movement . Is this possible? For reference, using a D7100 and a godox tt685N