A man and woman have both been arrested in connection with the murder of Lee Pomeroy, 51, who was stabbed to death on a train in Surrey.
British Transport Police said Darren Shane Pencille, 35, was charged with murder while Chelsea Mitchell, 27, has been charged with assisting an offender.
Pencille, of Willbury Road, Farnham, will appear at Staines Magistrates Court on Monday accused of attacking the father as he travelled between Guildford and London with his 14-year-old son.
The defendant was also charged with possessing an offensive weapon.
A police manhunt led officers to a flat in Willbury Road, where both of the accused live, on Saturday morning and they made two arrests.
Detectives said that Mr Pomeroy became locked in a three to four-minute row that escalated into an unprovoked, violent attack on Friday.
The married father, who would have celebrated his 52nd birthday yesterday, was described as being an honourable man and would always help somebody who was in trouble by his family.
He lived in Guildford with his 50-year-old wife Svetlana Pomeroy and their teenage son.
He was a devoted family man and did everything for his family, they said.
After the attack, the killer fled the train at Clandon station and headed in the direction of Dedswell Drive.
Police had been looking into whether he had managed to evade them by being picked up by a female friend in some woods.