Yesterday while I was at school I went to one of my clubs for our potluck. About ten minutes into our meeting they called a lock-down over the intercom and said that there was a man with a firearm on campus making threats, so we all hid under desks, turned of the lights and locked the door. Everyone was super scared. The teacher in the room even texted his husband saying "If anything bad happens remember that I love you". Fortunately, nothing bad happened, but lately I have been really paranoid, anxious and stressed. Even the smallest sound could set me off. Does anyone have any advice on how to deal with this.

try to talk to your friends,maybe check out school security to show how safe it is. I mean I had a lockdown too,but I wasn't really that scared

Talk to a therapist, a favorite teacher, a friend, or even a relative you're really close to. Having someone to talk through your problems with can really help calm your mind and your soul.

If there is a counselling service for school children in your country, then you should sign up for it. England has camhs and younger minds, though it doesn't sound like you are in England. A quick google search will tell you if there is, and if there isn't tell your parents that you need help. It sounds like you have PTSD.

I get paranoid too, I deal with it by doing something to take my mind off what ever it is that I don't want to think about, like by playing video games, watching TV or talking to friends. If you are in school when it happens then I would just pay attention to the lesson that is being taught