"It basically said students at Mendota High school, this is a warning, be careful you are in danger and it was in Spanish," said Mendota Police Chief Jerry Galvin.
Following the announcement around 7:10 Tuesday morning, there were some tense moments at the school as the Fresno County Sheriff's Bomb Squad fired two shots at the package.
"You might have heard the noise, which was their robot shooting about 850 pounds per square inch, a water shot into the device," said Galvin.
Galvin said a teacher discovered the mysterious package outside of a classroom near the science building, prior to the start of school and immediately alerted authorities.
"Just the material itself, it was covered in red tape and there were some exposed wires. Then with the sign attached that said, "You're in danger," we'd rather err on the side of caution," said Mendota High School Principal Carlos Arredondo.
Arredondo, said when the teacher came to his office around 7 o'clock to report the threat, he immediately evacuated the campus. About 50 students were moved to the football field and were bussed back home about a half an hour later, once classes were cancelled. An alert also went out to the parents of the other 700 students instructing them not to come to school.
"We deployed a robot to do a little recon, set up a disruption shot using water on the robot. It ended up being a bundle of wood wrapped in red tape with wires exposed. It was a hoax device," said Lt. John Reynolds, a member of the Fresno County Sheriff's Bomb Squad Unit.
A hoax device, he said, but a legitimate threat. For that reason authorities took the message seriously.
We're seeing violence everywhere, we're not immune to it. People here in the Valley think because we haven't had anything major yet, that we're safe. We're not. It just takes one crazy person to set things in motion here," said Reynolds.
Galvin added, "A prank is a prank, but when you get to the situation where you're closing a school, calling out all the emergency resources and you have a simulated device, this is something not on a whim, it isn't a phone call that a kid made because he doesn't want to take a test. This is much more serious when you simulate a bomb."
Police say the sign attached to the device appeared to be handwritten and included some initials that may provide them with clues as to who is responsible.
The campus is back open and students are expected to return to class Wednesday morning for a half day.