Does PTSD only come from major things like sexual abuse or being robbed etc

or could it be from an incident that happened with someone you trusted and saw as a friend, totally blindsided you and did a complete 180... and you had no idea how to cope

i ask because an incident like his happened to me in 2014 but I've never talked about it, i tried to wish it away and sadly, i still run into this person on a regular basis and still feel complete terror and like i may pass out or throw up. i do anything i can to avoid them but sometimes its unavoidable so i go into panic mode.

i plan to talk about this in therapy next week, it will be the first time I've told anyone but i just was kinda thinking if maybe this could somewhat be my issue since its been 3 yrs and i still feel terrified of this person.