From a 2013 interview with Spike Lee:
THR: How did you come to decide it should be a documentary over a narrative film? Why did you make that change?
Lee: Because it was a dumb idea when I wrote that letter to do it as a fictional account. It had to be a documentary. I didn’t want actors recreating the stuff. I wanted the parents, the mothers, the fathers, the sisters, the brothers. I wanted documents of them. I did not want this to be actors doing this. I wanted this to be a documentary.
THR: 4 Little Girls was your first documentary. It must have felt like a huge undertaking.
Lee: Documentary is storytelling. So I don’t really, to be honest, have a different mindset between my narrative and my documentary filmmaking. It’s about storytelling.