Thousands of commuters from the Thames Valley area were stranded in London after a man suspected of fatally stabbing a woman died on a rail line.
First Great Western services out of Paddington station came to a standstill after the man was hit by a train at Hanwell station, west London.
About 20 minutes earlier, police had received reports that a woman had been killed in Ealing, west London.
Train services were delayed for several hours on Thursday evening.
Trains travelling into Paddington terminated at Reading Station, Berkshire, where passengers were being transferred to a half-hourly service into Waterloo.
Lorraine Leaney, spokeswoman for First Great Western, said: "It's peak time travel and people will be making their way into London and out of London, so it will affect a large number of people.
"Police have sealed off the area of track where the death has happened.
"It's definitely going to be impacting on our services for the next few hours, how much longer after that I can't say."