Workers at 250ft tall office block had to run for cover when a man threw fire extinguishers, computers and chairs through a 10th floor window.
The man is understood to have set the fire alarm off at the 17-storey Castlemead building in Bristol and made his way up as staff were evacuated.
He then ran amok, wrecking computers and smashing doors and windows before hurling office equipment including desks and a printer into the street below. Most of the debris landed on the canopy of the reception area but several people and a number of firefighters were injured.
Police arrested a 49-year-old man at the scene on suspicion of burglary and common assault after he was restrained by a fireman and a Castlemead security guard. He was released on bail pending further investigation. The investment firm, Equiniti, attacked during the rampage said it did not believe the man arrested was a former member of staff.