A thief stole a man's wallet as he lay dying at Hastings railway station, police have said.
David Lovett, 66, collapsed after going into cardiac arrest just before 22:30 BST on 25 August. He died at the scene despite the efforts of paramedics.
Mr Lovett's son, Rich, said he was shocked and disgusted by the theft, and appealed for anyone who knew the suspect to contact police.
Detectives have released a CCTV image of a man they want to speak to.
Mr Lovett had been estranged from his father for 20 years, and the theft of the wallet meant it took a long time for the family to be informed of his death.
He said its contents could have indicated whether his father had thought of him and his brother.
"I don't know if he kept any photos in that wallet... it would just show that he still thought of us, and I'll never know whether or not that was the case," Mr Lovett said.