Need help contacting Austrian authorities

I have been exposed to someone on a social media platform that has illegal weapons in a other country (person in question lives in Austria) and is plotting crimes. Said person also supports Adolf H and has very extreme political views. I was sent videos with these weapons but they are since deleted. I know that this person has had problems with Austrian authorities in the past but I feel it’s necessary for them to know more. I did not want to see these videos and had not talked to this person in several years and have only known them online

This person is supposedly plotting something in another country and I am genuinely concerned. I do not want to get into any more details for my own safety if this person were to see this post in some way

Where do I contact the Austrian ”FBI” or police? I’m confused on what email to send it to