• The leader of Thowheeth Jama'ath, Mohammed Zaharan, is a well-known extremist who has spent time both in India and Sri Lanka and has preached hateful messages online in recent years.
• The Sri Lankan government acknowledged that more than ten days before the attacks, a foreign intelligence service had warned the country's security officials about possible threat to the churches by Thowheeth Jama'ath.
• That the country's security agencies have not responded aggressively to the warnings is called a "colossal failure of the intelligence services" and has led to a crisis for the government.
• Within hours of the bombing, Sri Lankan security services arrested at least 24 suspects, suggesting that the government knew where key members of Thowheeth Jama'ath could be found. The group was under surveillance, and the authorities had learned as early as January that radical Islamists who were possibly tied to the group had weapons and detonators in store.
• A forensic analysis of body parts found that most attacks were carried out by single bombers, but two men attacked the Shangri-La Hotel in Colombo.
• One of the suicide bombers was arrested a few months ago on suspicion of destroying a Buddha statue, a highly provocative act in Sri Lanka, a Buddhist island nation in the Indian Ocean.
• In Washington, intelligence and terrorism researchers investigated possible links between the Islamic state and the attackers, but had not yet reached their final conclusions on Monday afternoon.
What do we know about who was killed where?
• The attacks took place on Sunday morning in three churches and three hotels in three cities around the island. Two more explosions occurred in the afternoon in and around Colombo, one in a small guest house and the other in the seemingly safe house of the suspects. In this explosion, three officers were killed in search of the attackers.
• The deadliest explosion appeared to be in St. Sebastian's Church in Negombo, about 20 miles north of Colombo, where at least 104 people were killed.
• At least 28 people were killed in the Zion Church in Batticaloa on the other side of the East Coast island. The shrine of St. Anthony, a Roman Catholic church in Colombo, was also attacked with an unknown number of dead. Witnesses described there "a river of blood".
• In addition to the Shangri-La, the Cinnamon Grand and Kingsbury hotels, also in Colombo, were also attacked.
What we do not know about the attacks
• How could a small, obscure group, known primarily for the desecration of Buddhist statues, fend off sophisticated, coordinated attacks?
• Which international terrorist networks or networks have helped with the attacks?
• The names of the suicide bombers and the 24 people detained in connection with the attacks.
• Why do Catholics appear to have been singled out by the bombing of a majority Buddhist nation with a large Hindu minority?
• Why the authorities have failed to take significant steps to prevent an attack after receiving reports of an imminent threat.
• What impact will the failure of the attacks have on the Government of Sri Lanka, where the President and the Prime Minister were already involved in a bitter feud?
• How many of the approximately 500 injured were in critical condition and what is the final death toll?