DUNEDIN, Fla. -- Sheriff's deputies conducting a child porn raid on a Florida home Wednesday found an arsenal of guns and explosives and a homemade silencer, along with a note promising "bloody revenge."

Investigators found the weapons -- including an AK-47 assault rifle, a 50-calibre pistol, a baseball bat with nails jutting out and 2,300 rounds of ammunition -- in a locked closet in the Dunedin, Florida, home where 24-year-old Randall Drake lived with his parents, Pinellas County Sheriff Bob Gualtieri said.

During a news conference on Thursday night, Gaultieri said that even more "troubling" is that investigators found aerial images of two schools and a water treatment plant in nearby Tampa. There was also the note written by Drake that promised he'll have his "bloody revenge" and "the world will burn burn."

"I don't know what his plan was," Gaultieri said. "He had all kinds of books and all kinds of gun powder and if he had taken those devices put them in something else and put a bunch of nails and screws and other things, he could have caused some serious damage. Because it's the shrapnel that hurts and kills everybody."

The sheriff said he notified law enforcement and school officials in Hillsborough County, but so far investigators believe Drake was working alone.

His parents told authorities they didn't know what he kept in his locked closet, the sheriff said. Drake had no criminal history. He was fired in 2015 from Florida Firearm Academy in New Port Richey after he came to work with guns strapped to his thighs, officials said. He also was an Explorer with the Tampa Police Department when he was younger.

Drake's parents told deputies he was homeschooled.

Gualtieri compared Drake to Las Vegas gunman Stephen Paddock in the way he seemed to be acting alone.

"These are the people who are most concerning to us," he said. "What we call the lone wolves, the sleepers who are out there, the people who are not on our radar, the people who have fallen under the radar or off of it. You don't know about them until they engage in devastating acts and kill a whole bunch of people."

The note deputies found in Drake's bedroom read: "My fury at those who imprisoned me shall be vast and without mercy. I shall have my bloody revenge, and then the world will burn burn."

The child porn investigation that led to the search warrant this week began in January, the sheriff said.

Drake faces felony charges of possessing destructive devices. He left jail on a $20,000 bond, but an attorney isn't listed on jail records.