Not giving him his Miranda rights means that they can ask questions without the answers being admissible in a court of law. It’s because of any potential danger that could happen soon that the suspect may know about. They can then talk about that without the fear of it being admissible in a court of law, which helps authorities track down any imminent threats. After any pertinent information is given, he is read his rights and anything said after those rights is admissible in court.