Colombo, Sri Lanka — In response to the Easter bombings, Sri Lankan President Maithripala Sirisena asked his defense secretary and national police chief to step down Wednesday. They're accused of failing to act on intelligence reports before a wave of attacks killed 253 people -- a revised death toll the health ministry in Sri Lanka released on Thursday. Authorities previously said at least 359 people were killed.

In new security camera video, two of the bombers are in the Shangri La hotel elevator. They both get out and moments later, the blast goes off. One bomber was Moulavi Zahran, the lone unmasked man in images released by ISIS. Two others were brothers, wealthy and well educated local men.

Secretary of State Mike Pompeo told CBS News the terrorists probably had outside help. "I will say that every indication is that this was at the very least inspired by ISIS," he said.

The fact that the attack happened at all is a growing scandal in Sri Lanka.

Muslim community leaders are frustrated because they said they pointed to Sri Lankan security forces toward specific extremist threats years ago. But the security forces did nothing. Now, mosques are closed and under armed guard.

"We are fearing a backlash," said Hilmy Ahmed, Vice President of the Muslim Council of Sri Lanka, adding they were fearful of being attacked.

Muslims are as shocked and saddened as everybody else on this island still grappling with the scale of this massacre.

Michael Morell contributed to this report.