Play fighting led to choking

My best friend (also my ex) and I were in the auditorium yesterday with barely a few people around. I started bothering him, giving him little slaps (when I say little, I mean LITTLE). He started doing it back but a little harder than I was. We basically continued & then it escalated to a point where he was literally grabbing my neck & as if we were actually fighting. I got up and left outside, he followed me and was telling me to apologize even though he was being rougher. I didn’t. So again, he started grabbing me by the neck & squeezing harder. At this point, I wasn’t even hitting him back or doing anything because this wasn’t what it was supposed to lead to. I was doing tiny slaps, like the kind of slaps you give someone to wake up (not hard, basically just pats on the side of the face). He did it at least 3 times separately. On the 4th time, I had a pencil & he tried to do it again, but I grabbed the pencil and wrote on his white shirt (he hates when he gets dirty). He stopped and shortly after, my dad arrived so I left. The whole choking purpose (according to him) was to get me to apologize but was I even that wrong?? He was the one doing things harsher & I even told him that’s not the way to get someone to apologize. I agree that I was wrong in starting it, that’s why i didn’t say anything about it but they were literally gentle, I don’t understand how it could’ve led to him fucking choking me