When students at the Massachusetts Institute of Technology come together to share their sadness, it is probably not surprising that they do so online.

That is where many moving tributes were posted to an MIT police officer purportedly killed by the brothers believed to be responsible for the Boston Marathon bombings.

The surreal week of events that began with those explosions affected not only the students at MIT, whose late-night studies were punctuated by the sounds of gunshots, but also tens of thousands of others in and around a densely packed area home to no fewer than 58 universities with a collective enrolment of more than 250,000 people.

Doubtless they would have preferred to forgo the lessons taught by the tragedy. But their responses to it have been widely praised, and many have said that the experience has only strengthened their resolve to enter such fields as medicine, law enforcement and journalism.

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There were at least 17 university students among the victims of the explosions on 15 April. Many of their peers were among the people who helped the injured and gave their phones and opened their homes to stranded runners, and whose photographs and videos aided the investigation.

¡°They were thrust into an adult role, maybe for the first time, and, astoundingly, life and death was in front of them,¡± said Colin Riley, spokesman for Boston University.

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The marathon takes place every year on Patriots¡¯ Day, a Massachusetts holiday commemorating the first battles of the American Revolutionary War, and throngs of students take advantage of a break in classes to run or cheer.

One of those was Lingzi Lu, a 23-year-old mathematics postgraduate from Shenyang, China, who was completing her first year at Boston. She was watching at the finish line when the first explosion occurred. In the resulting confusion her roommate could not find her, so classmates searched the city until the university - after notifying Ms Lu¡¯s family - announced that she had been killed.

There was a spontaneous institution-wide candlelit vigil and a memorial service for faculty and students in Ms Lu¡¯s department. The university offered crisis counselling and seven members of its board of trustees pledged more than $560,000 (?368,000) for a scholarship in her memory.

¡°There isn¡¯t an individual at [the university] who didn¡¯t have some connection to people affected by the tragedy,¡± said Kenneth Feld, the trustee who proposed the scholarship.

The same could be said of any university in the Boston area.

Students from six campuses were among those injured, several of them seriously, including two from Boston University, seven from Emerson College, three from Tufts University, three from Northeastern University, two from Boston College and one from the Berklee College of Music.

Near the marathon¡¯s finish line, 50 Boston University pre-med undergraduates had been volunteering in the medical tent, filling out record forms and carrying supplies, when the bombs went off.

One, Yeon Woo Lee, was taking a breath of fresh air during a lull in proceedings when the first device exploded barely 20 yards away.

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¡°Everybody looked confused,¡± she said. ¡°A couple of seconds later, the second one went off. Suddenly we had organised chaos. People were wheeling [victims] in.¡±

Some of the Boston University volunteers worked to clear the aisles as the floor of the tent ran red with blood. They saw the wounded, including children, arrive with missing limbs, and physicians fashion tourniquets from belts and shirts. One was ordered to set up a morgue.

¡°There was nothing in a classroom that could have prepared us for this,¡± Ms Lee said. ¡°Some of the students in my group were barely 18. People stayed calm. Nobody panicked. It was scary, but I¡¯m glad that I was there to help out and very proud.¡±

The experience for her and the others, she said, was horrifying and inspiring. ¡°It was a terrible, terrible, terrible week with a lot of pain and suffering, but at the same time there¡¯s nothing else in the world I would rather do now than go into the field that I chose to dedicate my life to,¡± Ms Lee added.

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Spontaneous acts of kindness

As the bombs detonated, many marathon runners still on the course were stopped in their tracks by police and volunteers. At Boston College, which is on the route, students and employees started offering the competitors sweatshirts and blankets, plus mobile phones to call their loved ones.

The institution opened its chapel for the runners to keep warm and brought them sandwiches and water, while a club of student emergency medical technicians tended to aches, blisters and dehydration. ¡°It was just a simple act of kindness,¡± said college spokesman Jack Dunn. ¡°The kids just instinctively took them in.¡±

University students, Mr Dunn added, ¡°often get accused of being self- centred. The reality is we¡¯re always proud of our students, but never more so than because of the way they acquitted themselves on that day and during that week.¡±

As the week wore on, university presidents and chaplains went to the hospitals to console their injured students, shuttling back to campus to attend to the administrative problems caused by the attack: many schools remained closed the day after the bombings, with some final examinations being interrupted.

Students were among the many witnesses who provided video and photo footage to investigators as they narrowed their search for the bombers, while university police departments also contributed manpower.

But nerves were frayed once more when gunfire was exchanged late on 18 April in the heart of the MIT campus in neighbouring Cambridge. Sean Collier, an MIT police officer, was killed when reportedly confronting Tamerlan and Dzhokhar Tsarnaev, the brothers later named as prime suspects for the bombings.

Hugely popular with graduate students, whose clubs he joined and for whom his jokes helped to ease the stress of late-night studying, Mr Collier was about their age - 26.

He liked stopping in at the research labs and asking about the work being done, chatting with students and offering his help.

¡°His grin was irrepressible,¡± one student writes on a website instantly set up in his honour and titled Memories of Sean. Another adds: ¡°He was alive in the world in a way that is too rare. I didn¡¯t fully appreciate at the time having someone coming by with fresh eyes, full of genuine enthusiasm and curiosity about what I was doing.¡±

Dzhokhar Tsarnaev, 19, was a student, too. He was majoring in marine biology at the University of Massachusetts Dartmouth, about 60 miles south of Boston, although he was reportedly failing many of his classes. He returned there two days after the explosions to use the gym and to sleep in his room.

When Mr Tsarnaev was identified as being linked to the attack, the institution¡¯s 4,300 resident students were evacuated and the campus shut down while investigators combed it for leads.

Back in Boston, as the search for him intensified, residents and businesses, along with universities, were locked down for 12 hours. The deserted city streets and campuses looked like something out of an apocalyptic science fiction film.

It ended as it began, in violence. Tamerlan Tsarnaev, 26, was killed on 19 April in the shoot-out with police, while his younger brother was seriously wounded during his later apprehension. When it was over, students emerged and started looking for ways to cope with their anger, sadness and frayed psyches. They planned to give blood and filled out sympathy and get-well cards. They poured into religious services, vigils and memorial events.

Among them were two Boston College undergraduates, Danielle Cole and Michael Padulsky, who suggested on Facebook that people walk the final five miles of the marathon route as a tribute. Worried that no one would come, they returned a few hours later to discover that thousands had signed up (although the march has now been postponed).

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¡°I¡¯m just so inspired by how Boston has reacted,¡± said Ms Lee. ¡°I¡¯m really proud to be part of the Boston College community for the way it responded.¡±