The pileup of fiascos began long before the attack itself.

Elders in the town of Kattankudy had warned authorities several times over the past couple of years about the violent extremism preached by Zaharan Hashim, the suspected mastermind of the bombings on Sunday, who routinely called for the slaughter of nonbelievers.

Even after his band of radicals had begun targeting moderate Sufi Muslims and vandalizing Buddhist statues, the warnings were not taken seriously. Mr. Zaharan remained at large, and is believed to have traveled freely in and out of the country.

He fell on the radar of Indian intelligence agents who, in the weeks leading up to the attack, repeatedly told their Sri Lankan counterparts their concern that Mr. Zaharan was plotting violence. Some officials believe the Americans also had information on Mr. Zaharan, which they likely conveyed to the government.

Ten days before the bombings, a top Sri Lankan police official sent a detailed memo warning the security services that Mr. Zaharan’s little known militant group, National Thowheeth Jama’ath, was planning suicide attacks against churches.

Again, the government ignored the warning.

The political finger-pointing began while the bodies were still being collected. In the hours after the attack, President Sirisena and Prime Minister Ranil Wickremesinghe each said they were unaware of the warnings and blamed others for their ignorance.

How could Mr. Wickremesinghe have known, he asked, according to cabinet ministers allied with him, since the president had not allowed him in National Security Council meetings for months.