Cambridge resident Dzhokhar A. Tsarnaev, 19, has been named as the man being hunted by thousands of police officers and other law enforcement personnel as a suspect in the Monday bombing of the Boston Marathon; and the Thursday night fatal shooting of an MIT police officer, a carjacking and literally explosive car chase into Watertown.

Tsarnaev is considered the “second suspect,” with the “first suspect” in the bombing and crime spree that led from Thursday into Friday and from Cambridge into Watertown dead at Beth Israel Deaconess Hospital. That was believed to have been Tsarnaev’s older brother, Tamerlan, 26, who was wounded from gunshots and an explosive device he carried or “suicide vest” he wore, according to police.

The remaining brother could be wearing a “suicide vest” as well, police said. The numbers of law enforcement personnel searching for the suspect, possible accomplices, explosive devices or tracking down leads numbers between 6,000 and 10,000.

The hunt remained intense in Watertown well into its 10th hour, while Connecticut State Police suggested the suspect might be driving a gray Honda CRV with the Massachusetts license plate 316 ES9 and police surrounded an Amtrak train looking for a third suspect, according to journalist Michael Skolnik.

About an hour earlier, other law enforcement officials moved on the brothers’ home on Norfolk Street near Inman Square, warning that the area could be dangerous as well.

At 7:30 a.m., the street had been blocked at each end, as seen in this photo tweeted by The Boston Globe’s Wesley Lowery:

At about 7:45 a.m., a woman was taken by police from an apartment on the street, Lowery reported. NBC has reported that seven explosive devices were recovered over the hours in Cambridge and Watertown before the Norfolk Street area was cleared at about 5:30 p.m. Friday.

The Tsarnaev name arose in an Associated Press report about an hour earlier, but some nine hours after the drama began Thursday. It essentially replaced the naming of missing former Brown University student Sunil Tripathi over police scanner frequencies. Going against the bulk of the media – who’d seemed intrigued by the possibility Internet sleuths on sites such as Reddit could have named a suspect before investigators – NBC said the bombing suspects were from overseas and had military training, which would eliminate Tripathi.

The Tsarnaevs

The Tsarnaev brothers are said to be of Chechnyan descent, fleeing the nation’s bloody conflict in the early 1990s. (According to NBC’s Chuck Todd, Tsarnaev was born in Kyrgyzstan while older brother Tamerlan was born in Russia and became a legal resident of the United States in 2007.) The younger Tsarnaev was naturalized as a U.S. citizen Sept. 11, 2012.

The Tsarnaevs’  presence in the city seemed slight at first. As media scrambled for information on him, they found Dzhokhar Tsarnaev was a 2011 graduate of Cambridge Rindge & Latin School and wrestler who got a $2,500 city scholarship – and signed an online petition in February 2010 to let Cantabrigians keep chickens and ducks. His comment: a simple “Leave the chickens.”

“I’ve never seen that guy,” said a woman living in the apartment next to the suspects, Lowery said.

WBZ’s Lauren Leamanczyk found a friend of the brothers “shocked” to find the “popular” duo involved in such violence, though. And WCBV-TV reporter John Atwater reported talking to a high school guidance counselor who thought him “a normal kid,” goofy, mild-mannered and with plenty of friends.

As recently as Dec. 17 he retweeted an anti-gun image, saying “Don’t stop retweeting this! This has to change!” The image showed that in the United States automatic weapons were allowed and French cheeses were not.

His father, Anzor Tsarnaev, talked with The Associated Press from Makhachkala, Russia, saying:

My son is a true angel. Dzhokhar is a second-year medical student in the U.S. He is such an intelligent boy. We expected him to come on holidays here.

Dzhokhar Tsarnaev was a student at the University of Massachusetts at Dartmouth, where he returned Monday after the Marathon bombing. (The university shut down and was evacuated Friday.)

Tamerlan Tsarnaev had been a part-time accounting student and aspiring engineer at Bunker Hill Community College student for three semesters between 2006-08 and practiced boxing for the Golden Gloves at a Brighton gym, where photographer Johannes Hirn did a 2009 photo essay of him called “Will Box for Passport.” In the captions for the 15 photos, he is quoted as saying he was extremely religious and “don’t have a single American friend, I don’t understand them” – although he had a Portuguese-Italian girlfriend who converted to Islam. The site spotcrime.com, said he was arrested for domestic violence against the girlfriend in July 2009. He traveled to Russia for six months last year, according to the AP.

He dropped out of Bunker Hill Community College as he grew more religious, a family friend told The Wall Street Journal, but an aunt interviewed by The Toronto Sun told a different story, saying he left when he married “a Christian girl” and she gave birth to their daughter. He worked at several stores in the city, including delivering pizza, she said.

An uncle interviewed by Fox 25, Ruslan Tsarni of Montgomery Village, Md., said the older brother likely influenced the younger brother and urged Dzhokhar to turn himself in. “Everything you believe is wrong,” he said. “You murdered people, go and ask mercy.” He said he hadn’t been in touch with the brothers since 2009.

The site globalgrind.com says it has photos of Dzhokhar Tsarnaev from a social media site (with the man at left in the bottom photo not the older brother):

The photo of suspects posted by the FBI earlier in the morning, this time with Tamerlan Tsarnaev likely being the figure at right:

A very likely fake Twitter account in the name of Dzhokhar A. Tsarnaev saw its first tweet at 7:33 a.m., saying to Boston Police “I will kill you all as you killed my brother.” The account – which, again, is almost certainly fake – is here. (His real Twitter account, ignored since December, is mostly about sports.)

Reporting from the hours before Tsarnaev’s naming, including the shooting death of the Massachusetts Institute of Technology office, is here.

The MBTA said that at the request of the police all service is shut down Friday until further notice. There was to be no transport into or out of Watertown, as well, and residents of Cambridge, Watertown, Waltham, Newton, Belmont and Allston/Brighton and, as Gov. Deval Patrick stressed in an 8 a.m. press conference, “all of Boston,” where the suspect may be on the run, were reminded to stay indoors by police – some million people. It was also suggested that businesses not open, and Boston Police decreed at about 8:20 a.m. that taxi service also would be canceled for the day.

The bans on movement were lifted at about 6:10 p.m. Friday. Police said they believed Dzhokhar Tsarnaev was still in Massachusetts and warned people to stay vigilant and cautious.