Teenage thugs scattered planks they ripped from a fence across train tracks - then attacked a railway worker called to clear the line.
People living nearby had to step in to protect the man when he was set upon by the gang and pinned against a fence as they continued their deadly game.
Disaster was averted thanks to the bravery of local residents who chased off the youths before calling police and clearing the line.
Officers received a string of 999 calls from worried residents as the gang went on a rampage through Angmering village and station on Saturday evening.
People living in Warren Crescent, East Preston, went to investigate when they heard shouting and noise outside their homes.
They saw several gang members pin a railway worker against a fence, while other youths threw wooden posts on to the railway line.
One resident, who was the first to confront the gang, was watching television when she first heard shouting.
She said: "There were about eight of them, all aged from about 13 up to about 18. When I went out to have a look I saw they had a man pinned to a fence. I heard him tell them he was a railway worker.
"Kids were throwing planks of wood on to the railway track. I couldn't just stand there so I confronted them. Then they stopped and I picked up the bits of wood and brought them home."
Another resident was arriving home with his wife when they saw the gang walking down the road holding wooden posts with nails embedded in them.
The man said: "My wife and I just sat in the car for a while because we didn't know what was happening.
"At that point we didn't know a railway worker was being assaulted. It was only when we saw our neighbour go to confront them that we felt we had to back her up.
"They were goading her. There was no way we could let that happen."
The man said residents' lives were being made a misery by local gangs of youths.
He said: "It is getting out of hand. The police should do more. We hardly ever see them around here."
A man called the police at 9.20pm to say he had seen eight to 12 teenagers throwing planks which they had stripped from a garden fence on to the tracks.
At the same time, police were contacted by a man who said his teenage son had been assaulted by a gang at the station.
His son's face was slightly injured and police inquiries are continuing.
Police were contacted by other residents complaining of a gang causing general disturbance in the area such as kicking the front doors of houses.
Two youths have been arrested and questioned on suspicion of committing public order offences.
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