7 YEAR OLD SON WITH AUTISM WAKING SCARED OF BURGLARS??

Hi, I have a 7 year old boy with autism and moderate learning difficulties and ADHD, he is verbal but is understanding is not as good. He has never been a good sleeper, but over the last 3 days he has been waking up saying he can hear burglars down stairs, it is really distressing him. Every night I have reassured him and even taken him downstairs to show him there are no burglars in the house. I have CCTV cameras inside and outside my house, so I have even linked the internal cameras up to a TV camera in his room so he can see when he wakes in the night that there are no burglars.I asked where he got the idea, he said he heard it on the radio at school ( he goes to a special needs school) I have spoken to his class teachers but they can't think of anytime they have had the radio on since going back to school 3 days ago and they haven't discussed burglars. I don't know what to do to reassure him further. He is in tears at night and shaking terrified, it is breaking my heart seeing him like this. He also suffers high blood pressure which is under investigation and I am scared his blood pressure will get higher with the stress. Any advice would be appreciated!