Official: Boston attack originally planned for July 4th

BOSTON (CNN) --  Suspected bomber Dzhokhar Tsarnaev told investigators that the Boston Marathon was chosen as a target only a day or two before the event, a U.S. law enforcement official with first-hand knowledge of the investigation told CNN on Thursday. The official, who spoke on condition of anonymity, was not authorized to release the information to the public.

Here are the most recent developments in the investigation into the April 15 Boston Marathon bombings:

New developments:

-- The bombs used in the Boston Marathon attack were built in the apartment that suspect Tamerlan Tsarnaev shared with his wife and child, a U.S. law enforcement official with first-hand knowledge of the investigation told CNN on Thursday. The official was not authorized to release the information.

-- Suspected Boston Marathon bombers Tamerlan and Dzhokhar Tsarnaev initially planned to carry out an attack on July 4, but their bombs were ready earlier than they expected and they decided to move up the date, a U.S. law enforcement official told CNN on Thursday.

Previously reported developments:

-- The laptop computer belonging to bombings suspect Dzhokhar Tsarnaev has been turned over to the FBI by one of Tsarnaev's friends who has been charged with obstructing justice, Dias Kadyrbayev's lawyer told CNN on Thursday. A law enforcement source confirmed the attorney's account.

-- The body of Tamerlan Tsarnaev was picked up Thursday from the Office of the Chief Medical Examiner of Massachusetts, a spokesman for the office told CNN. Tsarnaev's cause of death will not be made public until the death certificate is filed with Boston's city clerk's office, Terrel Harris said.

-- The Kazakhstan Foreign Ministry said it was offering consular services to Kadyrbayev and Azamat Tazhayakov, who were charged with obstructing justice in connection with the marathon bombings. "We would like to emphasize that our citizens did not receive charges of involvement in the organization of the Boston Marathon bombings. They were charged with destroying evidence," the ministry said in a statement.

-- Katherine Russell, widow of Tamerlan Tsarnaev, spoke to her husband after his picture appeared on national television as a suspect, two sources familiar with the investigation told CNN on Wednesday. The nature of the conversation remains under investigation, but the sources said there was some concern that Russell spoke with her husband but did not call authorities who were still seeking to identify the men in the photos.

-- Authorities said Wednesday that three additional suspects have been arrested in connection with the Boston Marathon bombings. The three men are accused of helping one of the bombing suspects, Dzhokhar Tsarnaev, after the April 15 attack, according to federal prosecutors.

-- An attorney for Kadyrbayev, one of the three 19-year-olds arrested Wednesday, disputed the allegations against his client and said Kadyrbayev did not know items he admitted to discarding "were involved in a bombing."

-- Another of the suspects arrested Wednesday, Azamat Tazhayakov, is "shocked and horrified" to hear that someone he knew was involved in the bombings, attorney Harland Protass said. The attorney said his client has fully cooperated with authorities in the investigation and looks forward to the truth coming out.

-- Attorney Raymond A. O'Hara, who reportedly was appointed to represent Robel Phillipos, told CNN that the 19-year-old U.S. citizen has retained private counsel.

-- Kadyrbayev and Tazhayakov, who the FBI said are Kazakh nationals, and Phillipos were ordered Wednesday to return to court on May 14 for an evidentiary hearing, at which time a bail application is expected to be made.

-- About a month before the marathon attack, Dzhokhar Tsarnaev had told Kadyrbayev and Tazhayakov "that he knew how to make a bomb," according to an FBI affidavit recounting the charges. Kadyrbayev told investigators that Tsarnaev "appeared to have given himself a short haircut" two days after the bombings.

-- According to the affidavit, when the FBI on April 18 released photographs of bomb suspects later identified as Dzhokhar Tsarnaev and his older brother Tamerlan, Kadyrbayev texted his friend Dzhokhar to tell him "he looked like the suspect on television." Tsarnaev texted back "lol" and added, "come to my room and take whatever you want." Phillipos, Tazhayakov and Kadyrbayev went to the room, where Kadyrbayev noticed a backpack containing fireworks that had been "opened and emptied of powder," according to the affidavit.

"Kadyrbayev knew when he saw the empty fireworks that Tsarnaev was involved in the marathon bombing," the affidavit states.

-- Kadyrbayev and Tazhayakov are charged with "conspiracy to obstruct justice by conspiring to destroy, conceal and cover up tangible objects belonging to suspected Marathon bomber, Dzhokhar Tsarnaev, namely a laptop computer and backpack containing fireworks," according to the criminal complaint, released by the U.S. Attorney's Office, Massachusetts District.

-- Phillipos is charged with "willfully making materially false statements to federal law enforcement officials during a terrorism investigation," according to the complaint.

-- According to the affidavit accompanying the complaint, Kadyrbayev and Tazhayakov are both nationals of Kazakhstan who entered the U.S. on student visas.

-- Kadyrbayev, Tazhaykov, Phillipos and Tsarnaev began attending UMass Dartmouth at the same time in 2011, according to a criminal complaint filed by the FBI in U.S. District Court. Investigators originally thought Kadyrbayev was a student at the Massachusetts Institute of Technology; a screen grab of his Facebook page had him listed as being in MIT's class of 2015 and that he was in the school of engineering.

-- Murat Kadyrbayev, father Dias Kadyrbayev, said last week that his son and Tazhayakov own a BMW that garnered attention in the investigation. The car had a decorative license plate reading "Terrorista #1." The plate was a joke from friends in Spain, Murat Kadyrbayev told the Kazakh news website Tengri News and STV channel in an interview, Tengrinews.kz reported.

-- One of the reasons Kadyrbayev was of immediate interest involved activity on his Facebook page. The source says that while Dzhokhar was on the run -- at 3 a.m. on April 19, Kadyrbayev deleted a photo showing him and the suspect having dinner together, according to the source briefed on the investigation.

-- A federal law enforcement official told CNN the charge of conspiring to obstruct justice relates to their moving things from Dzhokhar Tsarnaev's dorm room and throwing them into a dumpster. The source said the objects disposed of included fireworks inside backpacks. The trash bin subsequently was taken to a nearby landfill. Authorities carried out a two-day search of the landfill in New Bedford late last week.