When T.J. Neely came home to Minneapolis from prison recently, he shut down his Facebook page. All of his friends and connections deactivated. To many, this may have seemed like social suicide, but Neely described it as simply a way to build a new life.

Neely, 25, got caught up in a lot of online drama as a former gang leader. Fights would often start on social media, which led to more tension building up in real life.

"I used to post random things, like, 'I'm here, looking for some friends.' But really, all I did was open my door for the wrong kind of attention," he said.

After deactivating his old page, Neely is building a new one and admitting only the friends he trusts.

"I doubt that I have even 100 friends now," he said. "I don't think I've even broken 50 yet."

Neely's experience shows how social media can make bad things worse, and how young mistakes can last in cyberspace forever. It's not just friends who see what you post. It could be your high school counselor, the admissions office at the college you want to attend, or the company you want to work for.

Former gang leader T.J. Neely shut down his old Facebook page when he left prison. He’s building a new one and admitting only the friends he trusts.

It could even be the police.

In the Minneapolis Police Department's strategic information center, one wall of a large, dimly lit room is lined with screens from ceiling to floor, along with computers spaced throughout. Seven days a week, 24 hours a day, police watch feeds from security cameras and monitor "chatter" on social media, especially among local gang members.

"When there's a high-profile event … kids talk about it. They talk about it not just face-to-face, but they talk about it online," said Lt. Jeff Rugel. "Particularly in gang shootings when they start talking back and forth … and dropping hints that I want to retaliate."

How do police infiltrate social media networks? Sometimes they create online personas and pretend to be someone else, Rugel said. Sometimes people who know gang members share information with police.

"None of the social media sites give us any special access," he said, adding that they don't use special programs or hackers.

Instead, police assemble information based on a user's history and threats being made, particularly about retaliation or people accused of being snitches. When his staff members see threats of retaliation, invitations to big house parties or other concerns, they pass that information onto patrol officers.

Police also see a lot that they can't use, he said.

"It's double-edged. … We have more access to some types of information," Rugel said.

"But there's a ton of useless information, a whole bunch of bragging."

A common trend on Facebook involves "prolific shoplifters holding up brand-new designer purses, designer jeans," he said. Sometimes, shoplifters even post prices and invite people to send orders.

But police can't use Facebook photos to arrest and charge the shoplifter if they don't know where the clothes came from or where the thief is keeping them, Rugel said. Instead, the information merely allows police to keep a closer eye on the shoplifter.

Postings on social media can also be used for more than crime prevention.

When two high school football players raped an intoxicated 16-year-old girl in Steubenville, Ohio, last August, one of the assailants videotaped the crime and shared it on social media. That video, along with the players' comments on social media afterward, became crucial as evidence in their trial.

The two young men were convicted on rape charges in March and sent to juvenile detention — a minimum of two years for the one who posted the video, a minimum of one year for the other.

For Neely, the days of finding trouble and potentially incriminating himself on social media are over.

Instead, he uses his new Facebook page to communicate with people like his mother and his sister — "my rock," he calls her.

He also posts inspirational quotes like "The bird sings before the light of the dawn" — a recent one that "is basically saying the bird has belief that the sun is going to rise. The sun isn't going to let me down."

His advice for young social media users: "It's all about the things that you say. If you say something that can get the wrong kind of replies, that's not a good thing for you. … But if you're a person who uses your posts to influence others or maybe to influence your way of thinking so that people can see the kind of person you are, then posting can be good."