According to the East Java Police, a premature explosion that took place at the Wonocolo low-cost apartment in Taman Sidoarjo on Sunday evening had involved a family – similar to the family of six that launched a series of deadly attacks on three churches across Surabaya earlier that same day.
The suicide bombings on Sunday morning killed 14 people and injured 41 others.
"They are the perpetrators, not victims," East Java Police chief Insp. Gen. Mahfud Arifin said on Monday as quoted by surya.co.id.
According to Mahfud, the family staying at the low-cost apartment had been planning an attack on an undisclosed target in Surabaya.
Police have identified the suspects as Anton Febrianto, 47, his wife Puspitasari, 47, and their four children, HR, 17, AB, 15, FS, 11, and GA, 10.
East Java Police spokesman Sr. Comr. Frans Barung Mangera said Anton was alive but had sustained severe injuries after the bomb prematurely went off, killing Puspitasari and their eldest son.
FS and GA also suffered severe injuries in the explosion; only AB was left unscathed.
"He [Anton] was holding a bomb trigger when officers arrived at the scene. Anton died after police officers decided to gun him down," Frans said.
Frans said AB was the one who later took his younger siblings to the hospital.
"Currently, the two are being treated at the Bhayangkara Police Hospital in Surabaya," Frans said, adding the bodies of Anton, Puspitasari and HR had been taken to the same hospital for an autopsy.
"We also seized several pieces of evidence, including packages presumed to be explosives," he said.
According to the low-cost apartment's administrative manager, Lidya Susanti, the family had been staying in Wonocolo since 2015. The parents had made a living by selling cakes.
The East Java Police said they were collecting evidence to find a link between Anton's family and that of Dita Supriyanto, who were behind the suicide bombings at Saint Mary Immaculate Catholic Church (STMB), Surabaya Pantecostal Church (GPPS) and the Diponegoro Indonesian Christian Church (GKI).