A pensioner came home to discover a torrent of water pouring through her ceiling after a hole was drilled through the wall into her attic.
May Addis, 79, thinks a hosepipe was pushed through the hole to flood her attic.
She spent yesterday mopping up and throwing out carpets and cushions which were ruined.
Mrs Addis, of Queen's Park Road, Brighton, has only just had her flat redecorated with a grant from the Royal British Legion's war widows' fund.
Her first husband, John Morris, was killed in action during a wartime campaign in Sicily.
The pensioner had popped out to the shops in the morning to fetch some mineral water and when she returned everything was fine.
She went out again on one of her regular visits to a nursing home in Bear Road, Brighton, where she helps out with odd jobs for the residents.
On her return she discovered floods of water pouring down the walls into her lounge and down the stairwell of the flat above the Videostar newsagents and video rental store, which she rents from the owners.
She said: "I didn't need any more water, did I? When I came back I got to the top of the stairs and saw there was water coming through the hatch to the attic.
"I made myself something to eat but when I went to sit down, everything was soaking wet.
"It was a real shock. I was shaking. It was terrible.
"The police and the council have been so good. The man from the council came and helped throw out all the carpets and the cushions. They are ruined."
Mrs Addis went downstairs to report the disaster to shop assistant Vera Dunkley, who contacted owner John Atkins.
Mrs Dunkley became frantic when the water started to flood into the shop, bringing down the ceiling tiles.
Mr Atkins, a director of the Videostar chain, hurried to the shop and climbed into the attic where he discovered two inches of water in the rafters.
His wife Julie said: "It's unbelievable. There was masses of water.
"It was just filtering down. It was running down the stairs.
"My husband started panicking when he got up there because he couldn't see any pipes that could be leaking.
"But then he saw the hole in the wall and he realised someone had drilled a hole through the wall. I've no idea why."
Mrs Atkins called the police but she was told officers could do nothing until she got a plumber to write a report verifying that the water had not come from a leaking roof.
She said: "We had to have a registered plumber to say in his opinion the roof was sound."
Police officers went to the building and found a hosepipe and drill in the flat next door.
A man was arrested.
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