The LAPD has been conducting an investigation into criminal activity -- possibly drugs or weapons. And someone who is at the house tells us cops may be attempting to put Charlie on an involuntary -- 5150 -- psychiatric hold.
UPDATE: Someone at the house tells us, one of the reasons the cops are there is because Charlie allegedly violated the temporary restraining order Brooke Mueller obtained ... which prohibits Charlie from possessing weapons.
UPDATE 10:42 PM THURSDAY Law enforcement sources tell us cops wrapped up their search and Charlie wasn't arrested. Charlie's lawyer, Mark Gross says police found one rifle -- from the 1800s -- and "a few bullets," adding no other weapons were in the house. Gross also confirmed police executed the search warrant because someone -- he didn't know who -- claimed Charlie and a gun.
Law enforcement sources tell us ... cops raided Charlie Sheen's house after receiving a call earlier today that Charlie threatened to harm himself with a firearm.
Under the restraining order obtained by Brooke Mueller, Charlie is prohibited from possessing weapons.
Cops are inside the house right now, searching for firearms and ammunition.
And law enforcement tell us cops are not trying to place Charlie on a 5150 psychiatric hold.
Charlie, his lawyers, and several friends are sitting at a table in the backyard eating hamburgers. KTLA shot video of the surreal scene from their helicopter.
The LAPD has been conducting several investigations involving Charlie, including the possible violation of the TRO.
UPDATE 10:18 PM PT THURSDAY -- Sheen just tweeted: "#fastball; the LAPD were AWESOME. Absolute pros! they can protect and serve this Warlock anytime!!! c"