A social media tit-for-tat sparked the rash of deadly shootings in Boston last week, according to sourceswithin anti-gang street units.

The Boston Police Department is still hoping for tips from the community to arrest whoever is behind the shootings across the city, in which one factor has been a common denominator: Facebook and social media are playing a big part in face-to-face violence.

It's the second time this year social media is said to have played a part in a deadly real-life confrontation. Sixteen-year-old Jonathan Dos Santos, who was shot and killed in June, told his basketball coach he was being pressured to join a gang on Facebook.

That, says Judith Donath, a fellow at Harvard University's Berkman Center for Internet and Society who studies social media and identity, is a real problem for young people.

"There's an enormous audience on social media, but it's also when you see people face-to-face, you might see five people have heard something you know, thats basically the limit," Donath said. "Online, it can extend in an infinite direction in both time and space."

And behind a computer or smartphone, it can be easy to say things you may not say in person.

"Online, things come off very aggressively," Donath said. "It's easy to be misunderstood. You may say something you don't think you meant in a nonaggressive way, and it can be taken that way."

Donath says there are pros and cons to social media — a pro being more information being available to police.

"There may be a lot of spaces, for instance, with gangs that they now need to also show off who they are and make some kind of position publicly," she said.

But police could be overwhelmed by the amount of online activity.

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