if you were here where i am threatening violence on another person then feeling awful after getting caught and punished for it is called guilt and remorse, not PTSD.

PTSD is when something something happens to you....

examples
someone threatened to do harm to you
someone physically abused you by hitting and such things
someone sexually abused you

and after these events you have nightmares, you have flashbacks, you have anxiety, depression in other words you have to have lots of problems because of someone doing something wrong to you.

the other way a person can have PTSD is if they witness something traumatic like seeing someone else get hurt, seeing or being a witness to a crime,

another way someone can have PTSD is if they know a close friend or family member has been harmed.

and the last way a person can get PTSD is through natural disasters.

but feeling bad after threatening someone else and then getting caught and in trouble for doing wrong is not PTSD. its having a guilty conscience and feeling remorse for hurting someone else.

my suggestion would be to not text the person you threatened, to stay away from them and have no contact with them. they probably did not tell you to leave them alone because of safety rules of not engaging in conversation and such with someone who they felt unsafe with. you know those basic rules schools teach of no talking to strangers and even if its someone you know, if they are threatening violence or you get that gut feeling of unsafe - ness to walk away and go tell. ...all those kinds of rules that schools now want students to follow. well this person who you threatened didnt do anything to you, what they did was what was taught. they walked away and told someone they trust, just like if someone walked up to you and said they were going to hurt you, you would also follow the rules by walking away and finding someone you trust and tell. basic safety rules.

Im not saying you dont feel bad about it, just that this person did what they were supposed to do when someone threatens to kill them. and you got caught. and now you feel bad about it.

maybe you and your therapist can set up a therapy session with you and this other person and your parents and the other persons parents and see if there is a way that you can accept responsibility for threatening to hurt the other person and help you and the person you threatened to feel better and safe around each other again.