A driver whose windscreen was smashed when a rock the size of a football was dropped from a bridge has spoken of her relief at her miracle escape.
Mother-of-two Lisa Horne, 26, said she believed that "somebody was looking over me" after she and her 48-year-old mother escaped unharmed when their Vauxhall Astra was targeted on the A12 in Essex last Thursday evening.
She said the perpetrator must be caught before someone is killed.
"Obviously, if I was going any faster, it may have been a different story. I do feel very lucky," she told a news conference.
"I am scared to drive, I don't think I will be driving in the dark. I certainly won't be going down the A12."
The incident happened under the Fryerning Lane Bridge near Ingatestone.
Ms Horne was driving to Chelmsford with her mother, Stella Horne, after a day's Christmas shopping at Lakeside Shopping Centre when the large piece of granite slammed on to their bonnet.
Forty minutes later, a 57-year-old woman was left with fractures to her face and ribs and internal injuries when a "bucket-sized" piece of concrete was dropped on to her vehicle from a different bridge on the same stretch of road between Chelmsford and London.
The second incident took place at 10.05pm as her car passed under West Hanningfield Bridge near Galleywood.
The woman, who is in a stable condition at Broomfield Hospital in Essex, was in the car with her husband, the driver, who suffered minor cuts and bruises.
Police are treating both incidents as attempted murder, and are investigating whether they have any definite links to more than 30 similar incidents on bridges along the A12 in Essex during the past three years.
Ms Horne said: "It has scared me a lot and it has made me realise how precious life is.
"I am scared that I may never have come home to my children."
She added: "I can't understand how anybody would do something like that. They are obviously not normal, they are not nice people, they need to be caught."
The pair had been travelling at around 50mph or 55mph at the time of the incident as it had been raining and Ms Horne was running low on petrol.
Her mother Stella said she remembered "a shadow coming down from the sky, and there was the biggest explosion".
"That was a rock hitting the car," she said.
"At the time I thought it was something off an aeroplane, that was the first thought that was in my head."
She said she was "so proud" of her daughter and how she handled the incident.
"I went into mum mode and started shouting," she said.
Asked what she thought of the perpetrator, she said: "I just don't know how they went home that night and slept, when they could have killed four people in half an hour. I can't sleep, thinking about it."
Detective Chief Inspector Keith Davies, of Essex Police, said there had been a number of leads and some good information which will help police to identify the person or persons responsible for the "very serious" incidents.
"I have still not as yet identified the location of where the first missile has come from," he said.
"But I would urge the community and the public to examine rockeries, gardens, to see if they are missing an obvious large lump of granite because I would like to identify that scene because that could provide some evidential opportunities too."
He added that a report last night of a man spotted with a piece of concrete on a bridge above the same stretch of A-road was a "false alarm".
Meanwhile, police in Shrewsbury confirmed that officers have launched an investigation after concrete blocks were dropped from a bridge over a busy road in the town.
Two motorists reported the incident, which happened shortly after 2am yesterday on a bridge crossing Robertson Way.
A West Mercia Police spokesman said: "Fortunately, no one was hurt but this could have resulted in a serious injury collision."