The alleged threat was made through a social messenger app called Kik.
In the threat, authorities say the teen said he was going to bring guns and "shoot up" Milford High School, and made reference to the shooting at Columbine High School in Colorado in 1999.
"The other students who saw the message on the Kik social media app were actually proactive enough to let their parents know; their parents then reached out to law enforcement; law enforcement worked with the school district," says Kimberly Root of Huron Valley Schools.
The student, whose name is not being released because he is a minor, was taken into custody.
"There is no such thing as a joke when you're talking about coming to shoot people. Not in this world, not in this time," says Oakland County Sheriff Michael Bouchard.
The Kik app is a way to text message, chat and share photos. Many social sites like this one are not monitored by creators. That's why watching your kids' activities on the Internet is so important, reminds Andrew Arena, who is formerly with the FBI and is now with the Metropolitan Crime Commission.
"Keep an eye on what sites your kids go on. Keep an eye on who they're talking to, and it's not just threats like this. It could be bullying. You're going to learn a lot about your kids by monitoring what they're doing," he says.
What made this teen's threat more serious is that authorities found multiple firearms were found at the boy's home, and have since been removed.
The teen is at Oakland County Children's Village awaiting possible charges.