CLERMONT, Fla. -- A student at a Seminole County high school was arrested for allegedly making a pipe bomb out of a pen and investigators also say he made threats against his school.

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SLIDESHOW: Images Of Sharpie Pipe Bomb
ARREST AFFIDAVIT: Clermont Homemade Bomb Case (PDF)

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If a teacher saw a Sharpie marker, she probably would think nothing of it. But this particular one had been filled with gunpowder and a fuse was attached. If it weren't for a text message the student sent, deputies may not have known about the very dangerous plot.

Michael Drnek, 16, is now facing felony charges for turning the Sharpie marker into a small bomb.

"It contained a large amount of gun powder and a fuse," explained

Deputies found the explosive pen inside Drnek's bedroom at his Clermont home on Thursday. It was locked in a little black safe, along with several smoke bombs. Drnek's father gave detectives a container of gunpowder he caught his son with days ago.

Investigators said Drnek sent another student at PACE-Brantley Hall School in Longwood a text message and picture of the device with the warning he was going to attack the school.

"The child who received the text message, his mother was looking at the text. She intercepted the message and then notified the Seminole County Sheriff's Office," Sgt. John Herrell, Lake County Sheriff's Office.

"Last person I would think of," said next door neighbor Judy Brown, who hired Drnek to do yard work and never imagined he'd be accused of bomb making. "He's a nice boy, never had any trouble with him. He's very polite."

PACE-Brantley Hall is a school for students with learning differences. Friday, officials gave each parent picking up their kids a letter describing what happened.

Drnek is being held in the juvenile detention center in Ocala. He's charged with possession of a destructive device with intent to do harm.