The teen was being held at a juvenile detention center facing three misdemeanor charges of juvenile possession of a handgun, said district attorney spokeswoman Pam Russell. He is due in court Feb. 27.
Police searched the boy's home after receiving a tip from Evergreen High School on Feb. 10, the same day he was suspended, officials said.
School spokesman Rick Kaufman said parents were calling with concerns and some kept their children home after photographs posted on the boy's profile on MySpace.com, a social networking Web site, began circulating through the community.
One photo allegedly showed him lying on a floor surrounded by nine rifles with the caption, "Angel o' death on wings o' lead."
"The photos were very disturbing, and while the content was not a direct threat, we just felt it was important for us to take appropriate disciplinary action," Kaufman said, adding the student could be expelled.
Evergreen High School is in the same district as Columbine High School, where two teenage gunmen killed 12 students and a teacher before committing suicide in 1999. One of the gunmen had posted a threat on the Internet before the shootings.
"In this case, it might turn out for the best that this young man was apprehended, regardless of whether he was posing a real threat or was just trying to show off," says CBSNews.com Technology Consultant Larry Magid. "Still, it demonstrates what we have been saying all along: What you post on your site can be held against you now and in the future."
MySpace has been under attack lately because many teens are posting personal information that would make it easy for sexual predators to find and prey upon them.
In writing about that on earlier this month, Magid said "Be very careful about photographs you put on your blog" and "Avoid postings that could embarrass you, your friends or family members now or later."
Such as being arrested for juvenile possession of a handgun.
MySpace.com has been banned from schools in Florida's eighth largest district, Polk County, reports . Officials barred the site after parents complained it could lure sexual predators, and that some teens go too far by posting revealing photos and discussing sexual activities or drug use.