• The leader of Thowheeth Jama's, Mohammed Zaharan, is a well-known extremist who has spent time in both India and Sri Lanka, and who in recent years has preached hatred messages online.
• The Sri Lankan government acknowledged that more than 10 days before the attacks, a foreign intelligence service gave the agency's security officers a detailed warning of a possible threat to churches by Thowheeth Jama.
• The fact that the security agencies of the country do not aggressively handle the warnings is to be called a "colossal failure on the part of the intelligence" and have created a crisis for the government.
• A forensic analysis of body parts showed that most of the attacks had been carried out by lonely bombs, but that two men had attacked the Shangri-La Hotel in Colombo.
• One of the suicide bombers was arrested some months ago with suspicion of having vandalized a statue of Buddha, a very provocative act in Sri Lanka, a Buddhist pluralist nation in the Indian Ocean.
• In Washington, intelligence and anti-terrorist investigators investigated possible ties between the Islamic state and the attackers, but from Monday afternoon no definitive conclusions had been reached.
What we know about who was killed and where
• The attacks took place in three churches and three hotels on Sunday morning in three separate towns across the island. There were two more explosions in the afternoon in and around Colombo, one on a small guesthouse and the other on what was supposedly safe house of the suspect. Three officers looking for the attackers were killed in this explosion.
• The deadliest of the explosions appeared to be in St. Sebastian's Church in Negombo, approx. 20 miles north of Colombo, where at least 104 were killed.
At least 28 people were killed at Zion Church in Batticaloa, across the island on the east coast. St. Anthony's Shrine, a Roman Catholic church in Colombo, was also attacked with an unknown number of dead. Witnesses described "a river of blood" there.
• In addition to Shangri-La, the cinnamon storms and Kingsbury hotels, also in Colombo, were attacked.
• At least 36 of the dead were foreigners, several of them American, the authorities said. Others were British, Chinese, Dutch, Indian, Portuguese, Japanese and Turkish nationals, according to officials and news reports.
What we do not know about the attacks
• How a small, unclear group, formerly best known for desecrating Buddhist statues managed to pull out of sophisticated, coordinated attacks.
• What international terrorist network or network, if any, helped with the attacks.
• Names of the suicide bombers and the 24 people in connection with the attacks.
• Why Catholics appear to have been designated in the bombings of a Buddhist majority nation with a significant Hindu minority.
• Why the authorities failed to take significant steps to try to prevent an attack after receiving reports of an imminent threat.
• What the effect of the failure of the attacks will have on the Sri Lankan government, where the president and prime minister were already involved in a bitter feud.
• How many of the approximately 500 wounded people were in critical condition and what the final death could be.