Revealed: The wealthy, well-educated brothers behind the Sri Lanka terrorist attack

In new security camera video, two of the bombers are in the Shangri La hotel lift.

They both get out. One goes into the restaurant,

Then his bomb goes off.

One bomber was Moulavi Zaharana, the lone unmasked man in images released by Islamic State.

He was a well-known YouTube radical preacher and well-known, too, to the government.

It's this sort of intelligence failure that prompted the president of Sri Lanka to demand the resignation of the defence secretary and chief of police.

Two of the bombers were brothers, wealthy and well-educated men, and the sons of a spice merchant.

One of the brothers owned a copper factory the police have raided twice. 

For that reason, it's speculated the factory is where they made the shrapnel for the bombs.

When police raided the family home the pregnant wife of one of the men triggered a suicide vest, killing herself, her two children and three policemen.

Thirty-two people are in custody and the country's churches are in lockdown but so too are mosques, with the country's Muslim population fearing a backlash. 

The island remains under curfew, but the government's made a hopeful promise of being in full control in a matter of days.