A suspect has been arrested by police hunting a knifeman who murdered a train passenger in Surrey as he travelled with his 14-year-old son.
The man was detained at an address in the Farnham area at around 6am on Saturday on suspicion of murder. A 27-year-old woman was also arrested on suspicion of assisting an offender.
British Transport Police said no-one else was being sought in connection with killing.
Detective Chief Inspector Sam Blackburn said officers were “confident to say that this is not believed to be a random assault.
“In the moments leading to the violent killing, both men appeared to be involved in an altercation lasting three minutes.
“Nothing justified the extraordinary violence that followed and we are concentrating our efforts on the on-going investigation.”
The son and other family of the 51-year-old man, who who stabbed multiple times, are being supported by specially trained family liaison officers.
Mr Blackburn, added: “We are continuing our appeal for information and I would urge anyone who was on board the train to contact us as soon as possible.
“Even if you did not witness the assault, it is vitally important we speak with you.
“Likewise, if you have any dashcam footage of the Clandon area after 1pm yesterday afternoon, we would like to hear from you.”
BTP Assistant Chief Constable Sean O’Callaghan said no-one else was being sought in connection with killing.
He said: “We now know from inquiries we’ve been doing overnight and from witnesses that the two men were involved in a verbal discussion, that discussion lasted three to four minutes, it moved through one carriage from where they first boarded into another carriage, and that argument escalated to the unprovoked violent attack that sadly resulted in the death.”
The attack happened on the 12.58 service between Guildford and London Waterloo on Friday.
The victim boarded the train at around 1pm at London Road station in Guildford with his son.
The killer, described as a black man in his 20s to 30s, approximately 6ft tall and of slim build with a beard, also boarded the service at London Road.
Police say the knifeman left the train at Clandon station and headed in the direction of Dedswell Drive. The train continued to Horsley station where police and paramedics attended.
A woman who lives in Clandon reportedly told other villagers that she had spoken to a “very sweaty and nervous” man in a field near her home afterwards.
Philip Herrington, the Rector of St Mary’s Church , West Horsley, visited Horsley train station on the afternoon of the attack and the following morning.
“I thought I’d come and bring some flowers because you don’t really expect anything like this to happen generally, not in a place like this, not on a midday train,” Mr Herrington said.
“It’s totally lamentable what happened and particularly for the young son to have witnessed what he witnessed.”
Mr Herrington spoke to British Transport Police at the scene of the incident on Friday and offered assistance to passengers.
He said: “British Transport Police officers were pretty shocked at what they’d seen as well.”