Not sure if this is the earliest memory but it's the earliest one I can give a somewhat exact date to. When I was around 3 years old, my preschool classmate got hit by a truck 2 meters in front of me. I remember my 2 other Japanese classmates were trying to hold him back but he ran into the street and bam, down he goes. My teachers found it weird that I didn't even run or cry when I saw it. Haha.