Manhunt for Boston bombers, Key developments in Boston bombings investigation

An officer carries a child away from an area where a suspect was hiding on Franklin Street on Friday, April 19, in Watertown, Massachusetts. After a car chase and shootout with police, one suspect in the Boston Marathon bombing, Tamerlan Tsarnaev, was shot and killed by police early Friday, and his brother and second suspect, Dzhokhar Tsarnaev, was taken into custody Friday night. The two men are suspects in the bombings at the Boston Marathon on April 15, that killed three people and wounded at least 170.








SWAT teams prepare to enter a home as they continue the door-to-door search.
SWAT teams continue the ongoing manhunt in Watertown, Massachusetts.

(CNN) -- The hours since the FBI released images of the two men suspected in this week's Boston Marathon bombings has been rife with new developments in the case. Among them:

Overnight drama:

-- Late Thursday, police respond to a call on the campus of the Massachusetts Institute of Technology, where university police officer Sean Collier, 26, was shot. He died from his injuries. Police believe the bombing suspects were responsible for the shooting.

-- Police say the two suspects hijack a car at gunpoint in Cambridge, Massachusetts, taking the driver as a hostage. The suspects tell the driver that they are the Boston marathon bombers, a law enforcement source said

-- The hostage is released at a gas station a short time later.

-- The two suspects pulled over to transfer materials into their new car, then threw one grenade and five pipe bombs at police chasing them, one FBI and one Department of Homeland Security official told CNN. Three of those explosives detonated, two did not, the officials said.

-- Police, who were tracking the vehicle using its built-in GPS system, pick up the chase in Watertown. The pursuit goes into a residential neighborhood, with the suspects throwing explosives and firing shots at officers, police say.

Officers fire back, striking a man later identified as 26-year-old Tamerlan Tsarnaev. The man -- who was suspect No. 1 in the images released late Thursday afternoon by the FBI -- was wearing explosives and an explosive trigger when his body was recovered, a source briefed on the investigation tells CNN.

-- Authorities later announce that they recovered a pressure-cooker bomb following the pursuit into Watertown, a source briefed on the ongoing investigation said. They also recovered a significant amount of homemade explosives" in Watertown, Massachusetts State Police spokesman David Procopio said.

Boston area locked down:

-- Around 2 a.m., police begin ordering Watertow (CNN) -- The hours since the FBI released images of the two men suspected in this week's Boston Marathon bombings has been rife with new developments in the case. Among them:

Overnight drama:

-- Late Thursday, police respond to a call on the campus of the Massachusetts Institute of Technology, where university police officer Sean Collier, 26, was shot. He died from his injuries. Police believe the bombing suspects were responsible for the shooting.

-- Police say the two suspects hijack a car at gunpoint in Cambridge, Massachusetts, taking the driver as a hostage. The suspects tell the driver that they are the Boston marathon bombers, a law enforcement source said

-- The hostage is released at a gas station a short time later.

-- The two suspects pulled over to transfer materials into their new car, then threw one grenade and five pipe bombs at police chasing them, one FBI and one Department of Homeland Security official told CNN. Three of those explosives detonated, two did not, the officials said.

-- Police, who were tracking the vehicle using its built-in GPS system, pick up the chase in Watertown. The pursuit goes into a residential neighborhood, with the suspects throwing explosives and firing shots at officers, police say.

Officers fire back, striking a man later identified as 26-year-old Tamerlan Tsarnaev. The man -- who was suspect No. 1 in the images released late Thursday afternoon by the FBI -- was wearing explosives and an explosive trigger when his body was recovered, a source briefed on the investigation tells CNN.

-- Authorities later announce that they recovered a pressure-cooker bomb following the pursuit into Watertown, a source briefed on the ongoing investigation said. They also recovered a significant amount of homemade explosives" in Watertown, Massachusetts State Police spokesman David Procopio said.

Boston area locked down:

-- Around 2 a.m., police begin ordering Watertown residents to turn off their cell phones.

-- At least 12 universities and colleges, along with Boston Public Schools and Cambridge Public Schools, announce Friday morning that they will be closed for the day due to police activity.

-- Authorities later Friday ask that people in Watertown, Boston and Cambridge -- where the two suspects lived -- not leave their homes, as authorities try to hunt down the remaining suspect.

-- The University of Massachusetts-Dartmouth -- where suspect No. 1, Dzhokhar Tsarnaev, was an enrolled student -- is evacuated. Law enforcement personnel swarm the campus, which is located just west of New Bedford and about 60 miles south of Boston.

-- Numerous activities scheduled for Friday night are canceled around Boston -- including Boston Red Sox and Boston Bruins games, as well as a Big Apple Circus show -- due to the ongoing manhunt for the marathon bombing suspect.

-- Amtrak train and Greyhound and regional Bolt Bus services were shut down. Taxi service across the city also was suspended for a time during the manhunt.

-- Around 6 p.m., Gov. Deval Patrick said that the lockdown had been lifted and that mass transit service had resumed.

-- About an hour later at 7:03 p.m., the Boston Police Department tweeted that there are "police operations" on Franklin Street in Watertown. CNN crew at the scene heard gunshots and saw several law enforcement vehicles race toward the scene.

The suspects:

-- The Tsarnaev brothers came from the Russian Caucasus region and moved to Kazakhstan at a young age before coming to the United States several years ago. Dzhokhar Tsarnaev was 8 years old at the time, their mother Zubeidat Tsarnaeva told state-run Russia Today from Dagestan.

-- A federal official told CNN that Dzhokar Tsarnaev came to the U.S. as a tourist with his family in the early 2000s and later asked for asylum. He became a naturalized U.S. citizen in 2012.

-- Dzhokar -- a University of Massachusetts-Dartmouth student -- was one of 45 high school seniors awarded a $2,500 scholarship by the Massachusetts city of Cambridge.

-- Tamerlan Tsarnaev was not a naturalized citizen, said the official, who spoke on condition of anonymity. He came "a few years later" and was lawfully in the United States as a green-card holder.

-- Tamerlan Tsarnaev studied engineering at Bunker Hill Community College just outside Boston, but had taken the year off to train as a boxer, sources told CNN.

-- In 2009, Tamerlan competed in a Golden Gloves match -- heavyweight division -- in Salt Lake City, losing in the first round.

-- Dzhokar Tsarnaev's friends expressed shock about his suspected involvement in the bombings, with his Cambridge Rindge and Latin high school classmate Eric Mercado telling CNN "there were no telltale signs of any kind of malicious behavior."

-- Larry Aaronson, Dzhokar Tsarnaev's neighbor and a former teacher at the high school Tsarnaev attended, described him as "caring," "jovial" and "so grateful to be here."

-- The mother of the Tsarnaev brothers refused to believe they were involved in the marathon bombings and subsequent shootout. "It's impossible for them to do such things. I am really telling you that this is a setup," she said.

-- Their father, Anzor Tsarnaev, told Russian state-run Zvezda TV, accused someone of framing his sons. "I don't know who exactly did it. But someone did," he said. n residents to turn off their cell phones.

-- At least 12 universities and colleges, along with Boston Public Schools and Cambridge Public Schools, announce Friday morning that they will be closed for the day due to police activity.

-- Authorities later Friday ask that people in Watertown, Boston and Cambridge -- where the two suspects lived -- not leave their homes, as authorities try to hunt down the remaining suspect.

-- The University of Massachusetts-Dartmouth -- where suspect No. 1, Dzhokhar Tsarnaev, was an enrolled student -- is evacuated. Law enforcement personnel swarm the campus, which is located just west of New Bedford and about 60 miles south of Boston.

-- Numerous activities scheduled for Friday night are canceled around Boston -- including Boston Red Sox and Boston Bruins games, as well as a Big Apple Circus show -- due to the ongoing manhunt for the marathon bombing suspect.

-- Amtrak train and Greyhound and regional Bolt Bus services were shut down. Taxi service across the city also was suspended for a time during the manhunt.

-- Around 6 p.m., Gov. Deval Patrick said that the lockdown had been lifted and that mass transit service had resumed.

-- About an hour later at 7:03 p.m., the Boston Police Department tweeted that there are "police operations" on Franklin Street in Watertown. CNN crew at the scene heard gunshots and saw several law enforcement vehicles race toward the scene.

The suspects:

-- The Tsarnaev brothers came from the Russian Caucasus region and moved to Kazakhstan at a young age before coming to the United States several years ago. Dzhokhar Tsarnaev was 8 years old at the time, their mother Zubeidat Tsarnaeva told state-run Russia Today from Dagestan.

-- A federal official told CNN that Dzhokar Tsarnaev came to the U.S. as a tourist with his family in the early 2000s and later asked for asylum. He became a naturalized U.S. citizen in 2012.

-- Dzhokar -- a University of Massachusetts-Dartmouth student -- was one of 45 high school seniors awarded a $2,500 scholarship by the Massachusetts city of Cambridge.

-- Tamerlan Tsarnaev was not a naturalized citizen, said the official, who spoke on condition of anonymity. He came "a few years later" and was lawfully in the United States as a green-card holder.

-- Tamerlan Tsarnaev studied engineering at Bunker Hill Community College just outside Boston, but had taken the year off to train as a boxer, sources told CNN.

-- In 2009, Tamerlan competed in a Golden Gloves match -- heavyweight division -- in Salt Lake City, losing in the first round.

-- Dzhokar Tsarnaev's friends expressed shock about his suspected involvement in the bombings, with his Cambridge Rindge and Latin high school classmate Eric Mercado telling CNN "there were no telltale signs of any kind of malicious behavior."

-- Larry Aaronson, Dzhokar Tsarnaev's neighbor and a former teacher at the high school Tsarnaev attended, described him as "caring," "jovial" and "so grateful to be here."

-- The mother of the Tsarnaev brothers refused to believe they were involved in the marathon bombings and subsequent shootout. "It's impossible for them to do such things. I am really telling you that this is a setup," she said.

-- Their father, Anzor Tsarnaev, told Russian state-run Zvezda TV, accused someone of framing his sons. "I don't know who exactly did it. But someone did," he said.