King said someone was using a computer or cellphone to watch him through the Nest app.
He said he walked into his living room to search for his cellphone or his iPad so he could turn off the camera, but he was unable to, because the other person had control of the app.
"I had no choice but to come right back inside and unplug the camera," King said.
Nest, which is owned by Google, provided WFTV with the following statement:
"Nest Security has not been breached or compromised. Customers may be vulnerable because their email addresses and passwords are freely available on the internet. If a website is compromised, it's possible for someone to gain access to user email addresses and passwords, and from there, gain access to any accounts that use the same login credentials."
Jason Cook, a Florida Department of Law Enforcement cybercrimes supervisor, said it is important to use a secured network.
"It's your thermostat. It's your home surveillance system, your washer and dryer, Wi-Fi, controlled outlet sometimes," he said. "They're all running through your network, and if your network isn't secured, all of that stuff is vulnerable."
Nest said that it encourages users to utilize its two-layer authentication process.
King said he is unwilling to put his privacy at risk again.
"I don't want to put my camera back up on the wall in fear it could be hacked again," he said.
The company spokesman would not estimate how many customers have experienced similar issues.