(NBC) - Parents dropped their children off at school Thursday morning, knowing the front door would be locked behind them. By the afternoon, the partial lockdown was over in Minneapolis public schools.
What remains is uncertainty and fear caused by someone on the other side of the world.
Authorities say the shooting threat came from Australia, nearly 10,000 miles from Minnesota. It was posted on a social networking site.
So how did police here figure out who posted the threat there?
"Everything does leave a trail at some point," says Det. Brian Hill with the Anoka County Sheriff's Office.
While Hill was not part of the investigation in Minneapolis, Anoka County has one of the most well-established computer forensics teams in the state.
Hill says it doesn't take much to track the source of an email or posting. Emails contain meta-data, hidden information you don't necessarily see unless you're looking for it. You can quickly find the address of the internet provider used by the sender.
Finding out the identity of the sender can be as easy as contacting the service provider.
Same with websites. They all log IP addresses. It's easy with a username and password.
Even if you enter false registration information, the IP address and your service provider can give you away.
"Every time it goes through a server it's stamping their information as it goes through to the end user," Hill explained. "All that data is important to find the original IP address."
Hill says, of course, there are some people who don't want to be found and technological know-how helps them hide, but that's where old-fashioned police work comes in with cops keeping pace with the criminals.
"Technology makes our lives easier in every aspect," Hill said. "It makes it easier for the non-law abiding citizens and it makes our jobs easier it's just a matter of staying one step ahead of them."