John McCready uploaded the footage to a Paranormal Facebook page in a bid to find out what others thought had set the sensors off.
The footage – captured around 11pm on January 24 at a surgery in Belfast, Northern Ireland – appears to show a shadowy figure in the bottom left corner of the screen.
The bizarre figure can be seen moving – or as John described “floating” – past the receptionist desk before gravitating towards the automatic front doors.
Around 40 seconds later, the doors swing open and set off another automatic light.
After posting the clip, he said: “I work for a security installation company in Belfast Northern Ireland, we were called out to the Bradbury Clinic in Belfast to see why they were having so many false alarms on their intruder alarm.
“My colleague carried out a playback of the CCTV system at the time the alarm was activated in the system log.
“He recorded what he saw on his phone.”
John claimed the intruder alarm was “also activated” during the bizarre encounter.
Since posting the video online, hoards of people have flooded in to view the clip.
One person said: “Wow! As it moves it looks like a small person shape, you can see what looks like legs walking I think, had to watch a good few times to see it, fascinating stuff!”
Another added: “Yes I see it, it’s like a round dark shadow.”
A third said: “It’s very weird but cool too.”