A disturbing flurry of text messages has revealed that Boston Marathon bomber Tamerlan Tsarnaev was willing to lay down his life for his Muslim faith.
It's the latest in a series of new revelations about the elder Tsarnaev brother, who was killed in a shootout with police in the early morning hours of Friday.
Little is known about Tamerlan in the months before the attacks, but his brother has confessed that they were self-radicalized and angry over the wars in Iraq and Afghanistan.
Fox News reported that in 2011, he sent text messages to his mother, Zubeidat Tsarnaeva, indicating that he was willing to die for Islam.
Around the same time he sent those texts, suspicions were brewing about the 26-year-old former boxer.
On Wednesday, U.S. officials described to the AP what the government knew about Tsarnaev since he was first placed on the intelligence community's radar 18 months ago.
The officials spoke on condition of anonymity because they were not authorized to publicly discuss the ongoing investigation.
Russia's internal security service, the FSB, sent information to the FBI about Tamerlan Tsarnaev on March 4, 2011.
The Russians told the FBI that Tsarnaev, an ethnically Chechen Russian immigrant living in the Boston area, was a follower of radical Islam and had changed drastically since 2010.
Because of the subsequent FBI inquiry, Tsarnaev's name was added to a Homeland Security Department database used by U.S. officials at the border to help screen people coming in and out of the U.S.
Killed: Tamerlan Tsarnaev was killed during a shootout with authorities in the early morning hours of Friday. Circled is a pressure cooker bomb similar to the ones detonated at the Boston Marathon
Mommy dearest: In 2011, Tsarnaev sent text messages to his mother, Zubeidat Tsarnaeva, explaining his willingness to die for Islam
That database is called the Treasury Enforcement Communications System, or TECS.
The FBI's Boston office opened a preliminary review of Tsarnaev and searched government databases for potentially terror-related communications.
Investigators looked into whether Tsarnaev used online sites that promoted radical activity.
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They interviewed Tsarnaev and his family members but found nothing connecting him to any extremist groups.
The FBI shared that information with Russia and also asked for more information on Tsarnaev, but never heard back. The FBI's review into Tsarnaev was closed in June 2011.
Then, in late September 2011, Russia separately contacted the CIA with nearly identical concerns about Tsarnaev.
Boston bombers: Dzhokhar Tsarnaev, left, and Tamerlan, right, are pictured near the finish line of the Boston Marathon, where authorities say they planted bombs that killed three people
The Russians provided two possible birthdates for him and a variation of how his name might be spelled, as well as the spelling in the Russian-style Cyrillic alphabet.
The CIA determined that Tsarnaev should be included in TIDE, and the National Counterterrorism Center added it into the database.
The spelling of Tsarnaev's name in TIDE was not the same as the spelling the FBI used in its investigation. The CIA also shared this information with other federal agencies in October.
A disturbing picture of Tamerlan Tsarnaev has emerged in the days since he was killed in a police shootout - a proud but angry young man who never quite achieved his own idea of the American dream, but found solace instead in a radical form of Islam adopted by fighters in his homeland.
What now seems clear is that he was deeply influenced by a few months' sojourn in Makhachkala, Muslim Dagestan's capital on the Caspian Sea, where children in the street play 'cops and guerrillas' and bombings and shootings are everyday news.
On the list: Tsarnaev's name was added to a Homeland Security Department database used by U.S. officials at the border to help screen people coming in and out of the U.S.
Tamerlan returned to Dagestan in 2012, where his mother and father had relocated after splitting up. Family members there who had not seen him for years were surprised by his new interest in religion.
His mother now speaks proudly of his apparent religious awakening, and says she does not believe he would have been capable of the Boston attacks.
'He changed when he started practicing Islam. He would read all the time,' she said. 'He had started going to nightclubs, but ever since I said to him that 'You are a Muslim, you should not do such things, they are haram', he became more religious," she told Reuters in English in Makhachkala.
During his stay in Dagestan, relatives say, he clearly stood out as an American, speaking Russian with a foreign accent and slipping into English when he could not remember a word.
'I don't think he was interested in friendships,' his mother said, adding that he followed lessons online in the Koran to try and understand it in its original Arabic.
'He was reading, always in front of the computer - he was taking classes on the Koran,' she said. 'He was very interested. He didn't want to read it in translation.
'He said, "Mama it's very difficult, but I want to do this." He really wanted to get into the true reading of the Koran. I was happy about that.'