Sensing that there was little chance of a reconciliation, the accused took out the knife and stabbed his lover twice in the chest and once in the back.
A passer-by - who remains unidentified - struggled with the accused, kicked the knife into a drain and scolded him before walking off.
A few other passers-by performed cardiopulmonary resuscitation on Tan before paramedics arrived. Mr Tan was pronounced dead in hospital at about 9.15am.
The accused, who was wailing about having killed someone, was arrested at the scene.