Lead was stolen from the roofs of homes in Cardiff over the weekend.
Admin assistant Gemma Hamilton, 32, of Llandaff, says she spotted someone on the ledge above her living room in the early hours of Saturday.
Mrs Hamilton, who had two children in the house, said she was afraid her home was being broken into.
"I couldn't believe my eyes," she said. "It took me quite a few seconds to register it was the back of someone's head with a hood up."
She said that she didn't make a sound for fear of what would happen next.
"I was thinking of the kids, I didn't want someone coming upstairs."
After the police arrived, she realised that some of the lead had been taken. Two houses nearby were also affected.
Another Cardiff resident, David Spragg, who lives in Gabalfa, claims he caught someone on his roof at 1300 on Saturday.
After hearing footsteps, Mr Spragg, 34, went to see what was going on, and explains: "I could just see a shadow of someone yanking away at something."
The pub worker then reached for a mobile phone, using the torch application to shine light onto the roof - prompting the perpetrator to run off.
Mr Spragg, who says the incident "took my breath away, I was just shocked", estimates that around five to six metres of lead were stolen.
He also said his neighbour had lead stolen from their roof.
A spokesperson for South Wales Police said: "On Saturday 1st September we received reports of the theft of lead from the roof of two properties in Cardiff.
"Anyone with any information can call us on 101 or call Crimestoppers anonymously on 0800 555 111, quoting reference number 1800332679 for the incident in Llandaff, or 1800332932 for the incident in Gabalfa."