Three others, including one of the suspects, who engaged responding policemen in a shootout, were also injured.
Victim Mary Gilbuena, also a resident of Baseco compound, died an hour later at the Gat Andres Bonifacio Hospital due to a gunshot wound in the head.
Based on the investigation by the Western Police District (WPD) Homicide Unit, the incident happened at about 5:30 p.m. at the basketball court of Baseco compound.
The community was almost wiped out last week after a 10-hour fire razed its shanties leaving thousands of families homeless.
Social workers immediately came to the aid of displaced families of the community known as a haven for criminals.
According to case investigator Senior Police Officer 1 Athos de Quiros, the suspects, mixed with the crowd who were receiving relief goods from barangay officials and social workers.
The suspect, identified as Nestor Caures, 23, of Del Pan, Tondo, Manila, reportedly posed as one of the fire victims but for still unknown reasons, suddenlty pulled out a .38 caliber revolver and shot the victim from behind.
Panic followed as other residents fled for cover and lawmen patrolling the area chased the suspect. After a brief chase, Caures was wounded and arrested.
The two others reportedly wounded in the incident were identified as Gerry Rondina, 18, who was hit in the right buttocks and Francisco Alegria, 28, who was shot in the left leg. Both victims are now in stable condition.