PS4 GTA V Online v Sony Pulse wireless headset

PS3 natively supports bluetooth.

Before you can use the Bluetooth headset with any device, such as the PS3 or a mobile phone, the headset must be paired to the desired device.

You can pair the headset in two ways:

Automatic mode (using the supplied USB cable) - Enables the headset's advanced features for the PS3. Using automatic mode, you can pair the headset with any PS3, but only the most recently paired PS3 will be saved in the headset's list of paired devices. Click here for more information on the advanced features of the Bluetooth headset.

Bluetooth discovery mode - Sets up the headset as a standard Bluetooth headset. By using Bluetooth discovery mode you can pair the headset with many other Bluetooth devices.

https://support.us.playstation.com/app/answers/detail/a_id/1226

Based on what you've described, it is likely that the online lobby you were in had a hacker/modder. These people are able to do a lot of crazy stuff, including spawning weapons that you can pick up.

These weapons that you've picked up should not persist between sessions, so re-starting the game or entering a new lobby should remove them from your inventory.

Rockstar has, thus far, been largely ineffective at stopping many of these hackers. But if you manage to capture video proof of someone hacking (often difficult unless they're being obvious), you should submit it to Rockstar support by opening a new support request.