To put all the silly eyewitness reports to bed, look at the flight log on FlightRadar. It starts of conducting multiple circuits at an airfield.
It departs the airfield and between 1500-1800ft on multiple occasions it has a high RoD, recovers and climbs back up to altitude.
Looks like circuits followed by Autorotation training, perhaps practise engine failure go resulted in the touch drills being the real thing