Much more information here:
http://www.thejakartapost.com/news/2018/05/13/surabaya-church-bombings-what-we-know-so-far.html
“No terror group has claimed responsibility for the attacks. But former National Counterterrorism Agency (BNPT) chief Ansyaad Mbai said the bombings in Surabaya could be linked to the riot that occurred at a detention center at the National Police’s Mobile Brigade headquarters (Mako Brimob) in Depok, West Java.
“The mastermind behind these incidents might be the same,” he said during a phone interview with Kompas TV.
The Islamic State has claimed responsibility for the riot incident at Mako Brimob, which led to the deaths of five members of the police’s elite counterterrorism squad, Densus 88, and a 36-hour standoff.”
“A witness reported that the alleged suicide bomber at GKI church was a woman who went to the church with two children.
“I heard two explosions, one was in the church’s parking lot and the other was outside the church. The woman was with two little boys,” Johanes, a member of the GKI congregation, told Kompas TV.
The police have yet to confirm Johanes’ statement.”