Is posting violent messages on Facebook and Twitter a sign you are a mass murderer? Some psychologists say we need to pay closer attention to our friends' cyber behavior.

Social media has been linked to mass shootings across the nation recently - with suspects posting warnings of possible attacks and violence on MySpace and Twitter, that law enforcement officials only discover after the incident.

"Is it normal to want to kill your all your co-workers?" That's the message Terence Tyler posted on this Twitter page twice, once two years ago, before he opened fire at an Old Bridge supermarket last week killing two employees and himself.

Jared Loughner, the man accused of the Tucson massacre that killed six and wounded fourteen others wrote, "Please don't be mad at me," on MySpace and took photos posing with a rifle hours before the shooting.

"What we're seeing is isolated cases of troubled people, who did reach out in some capacity," said Dr. Pamela Rutledge, director of the Media Psychology Research Center.

She says often times, mass murderers are looking for their fifteen minutes of fame, but its also tough to pinpoint if one of your cyber friends might actually be dangerous.

"Its very difficult to determine when you need to take action and when you don't, if you don't know the person."

Dr. Rutledge says we can't blame social media for these tragedies.

"We need to remember that social media doesn't change who people fundamentally are...it doesn't make someone who isn't violent, violent."

The bottom line, she says, is that any spoken or written threat of violence you see should be taken very seriously.

"We need to think about how much we want to monitor our friends online. If you know the person well and can decipher that message and clearly something is wrong, you need to take action."