


Azamat Tazhayakov, left, Dias Kadyrbayev, middle, with bombing suspect Dzhokhar Tsarnaev. Reuters

An affidavit filed in Boston federal court provided a new glimpse into Dzhokhar Tsarnaev's alleged activities between the April 15 bombing and his capture April 19. After allegedly plotting the attack with his older brother that killed three people and injured more than 200, the college sophomore seemed to resume his daily routine, hanging out with friends late into the night, offering a ride to a classmate and texting his buddies at the University of Massachusetts Dartmouth.

Two of the newly charged men— Dias Kadyrbayev, 19 years old, and Azamat Tazhayakov, 19—are nationals of Kazakhstan and, like Mr. Tsarnaev, are Russian speakers hailing from parts of the former Soviet Union.

The two were charged with attempting to impede the bombing investigation by throwing away a backpack containing fireworks that appeared to have had their explosive powder removed. Authorities believe the explosives used in the bombs were made with black powder that most likely came from fireworks.

Robel Phillipos YouTube

The third person charged Wednesday, 19-year-old Robel Phillipos, is a U.S. citizen and is accused of lying to federal investigators when asked about alleged destruction of evidence. The three aren't accused of aiding the bombings themselves or knowing about the plot ahead of time.

Lawyers for the two Kazakhs said their clients were cooperating with authorities and were shocked by the bombings. Robert Stahl, Mr. Kadyrbayev's attorney, said his client didn't know the backpack contained evidence linked to the bombing. Derege Demissie, attorney for Mr. Phillipos, declined to comment beyond saying that his client isn't accused of discarding evidence or any other offense related to the bombing.

Authorities allege that Mr. Tsarnaev, 19, and his brother, Tamerlan Tsarnaev, 26, carried out the twin bombings near the Boston Marathon finish line.

Dzhokhar Tsarnaev attended UMass Dartmouth with the three friends charged Wednesday. He is recovering in a prison medical facility from injuries suffered in his daylong getaway attempt. His brother died after a gunfight with police.

At a hearing Wednesday, Magistrate Judge Marianne Bowler read the charges to the men. They said they could afford attorneys. The lawyers for the two Kazakhs said the government was trying to deport the men and they opposed that effort. The judge chided Mr. Phillipos for looking down during part of the hearing, telling him he should be paying attention.

The two Kazakhs face up to five years in prison while Mr. Phillipos faces a maximum eight-year sentence if convicted.

The FBI affidavit said agents recovered Mr. Tsarnaev's backpack, enclosed in a black garbage bag, on April 26 from a landfill. Inside the backpack, they found fireworks, a jar of Vaseline and UMass Dartmouth materials for classes in which Mr. Tsarnaev was enrolled.

The FBI earlier found that the bombs were believed to contain a "low explosive powder extracted from commercial fireworks," according to an FBI lab analysis reviewed by The Wall Street Journal.

Investigators still are trying to determine where the brothers allegedly gained their bomb-making know-how. The FBI report said the bombs appeared to go beyond recipes in Inspire magazine, published by al Qaeda's Yemen affiliate.

Fireworks allegedly found in a backpack owned by Dzhokhar Tsarnaev. AFP/Getty Images

Months before the attack, a group of friends including Dzhokhar Tsarnaev and the two Kazakh suspects had set off fireworks together along the Charles River in Boston, the affidavit said, citing interviews with the men. A month before the bombing, while eating with his friends, Mr. Tsarnaev told Messrs. Kadyrbayev and Tazhayakov that he knew how to make a bomb, the affidavit said.

After the bombing, the friends continued to spend time together at UMass Dartmouth. The state university has only about a dozen students from Russia or other parts of the former Soviet Union, according to 2012-13 enrollment records, meaning three of the four friends were among the few native Russian speakers on campus.

Kazakhstan is a former Soviet republic where Russian is widely spoken and the populace is predominantly Muslim. Oil wealth has transformed the country in recent years, and many prosperous families send their children overseas for education. The Tsarnaev family lived in nearby Kyrgyzstan for many years.

Mr. Kadyrbayev, who had known Dzhokhar Tsarnaev since 2011, told investigators the two met briefly April 17 outside Mr. Tsarnaev's dorm, where Mr. Kadyrbayev noticed Mr. Tsarnaev's hair had been cut short.

Mr. Tazhayakov told the FBI that on April 17—two days after the bombing—he and Mr. Tsarnaev hung out until midnight at the apartment shared by the two Kazakhs. The following day Mr. Tazhayakov said he got a ride home from class from Mr. Tsarnaev.

But the Tsarnaev brothers' anonymity was soon to end. On April 18, the FBI released photos of the suspected bombers and Dzhokhar Tsarnaev's friends immediately thought they recognized him, the affidavit said.

Mr. Kadyrbayev told the FBI that when he saw the photos, he sent text messages to Mr. Tsarnaev saying he looked like one of the bombers. Mr. Tsarnaev responded jokingly "lol" and "you better not text me." Another text read "come to my room and take whatever you want."

The three men allegedly visited Mr. Tsarnaev's dorm room just over an hour after the FBI released the pictures, the affidavit says. Mr. Tsarnaev had left an hour earlier, a roommate told them, according to the affidavit. They spent time watching a movie before noticing a backpack containing fireworks shells, according to the affidavit.

Mr. Kadyrbayev knew when he saw the empty fireworks that Mr. Tsarnaev was involved in the bombing and also believed the Vaseline was used to make bombs, the affidavit said, citing interviews with him. Mr. Kadyrbayev decided to remove the backpack to help his friend, the affidavit said. He also took Mr. Tsarnaev's laptop, it said.

All three men returned to the apartment shared by Messrs. Kadyrbayev and Tazhayakov with the backpack and computer and watched news reports on the police manhunt for the Tsarnaev brothers. The three decided to throw the backpack and its contents into the trash "because they did not want Tsarnaev to get into trouble," the affidavit said.

The FBI has recovered the computer, a U.S. law-enforcement official said.

Mr. Kadyrbayev put the materials in a trash bin outside his apartment building. A garbage truck collected the trash the next day, the men told the FBI.

Mr. Stahl, the lawyer for Mr. Kadyrbayev, disputed that his client immediately suspected Mr. Tsarnaev was one of the bombers, saying that "his first inkling came much later."

The FBI affidavit alleged that Mr. Phillipos gave differing accounts in three interviews before admitting largely to the description of events provided by Messrs. Kadyrbayev and Tazhayakov to the FBI.

—Pervaiz Shallwani contributed to this article.

Write to Evan Perez at evan.perez@wsj.com, Jennifer Levitz at jennifer.levitz@wsj.com and Jon Kamp at jon.kamp@dowjones.com