Sri Lanka Bombings Live Updates: Victims Interred in Mass Grave as Dozens Are Arrested – The New York Times

But in the Sri Lanka attack, it appears that all seven suicide vests detonated and did heavy damage, Mr. Stewart said, indicating skill at making bombs and manually activated detonators, and suggesting access to a large supply of military-grade high explosives.

“You don’t do that by accident, so they must have a fairly decent logistics network and funding,” he added.

But Joshua A. Geltzer, a former senior director for counterterrorism at the National Security Council, said he would not be surprised if a small group had been able to stage the attack without direct help.

“There is so, so much instruction and guidance available on the open internet these days, not to mention whatever is circulating on encrypted chat groups, widely available in terrorist circles if not totally public,” he said.

Unexploded bombs, apparently not designed for suicide attacks, were found in other public places in Sri Lanka. That suggests that the bomb maker (or makers) was less expert at detonation using timers or remote control, Mr. Stewart said.