Gunman Arrested After Opening Fire Near Site of Clive Davis Grammy Party

Preparations for Clive Davis' famed pre-Grammy party came to a grinding halt Thursday morning as cops busted an armed man at the Waldorf Astoria ... TMZ has learned.

The Waldorf is right next door to the Beverly Hilton -- where Clive's event is held -- and cops swarmed the area after getting a call shortly after 9:30 AM for a disturbance at the hotel. We're told a drone was deployed over the Waldorf, and spotted the gunman standing on a hotel room balcony.

Cops immediately shut down one of all traffic around the intersection of Wilshire and Santa Monica Boulevard -- one of L.A.'s busiest intersections -- and deployed SWAT officers around the hotels.

Law enforcement sources tell TMZ ... cops made contact with the guy in his hotel room and convinced him to surrender peacefully -- but once inside, they discovered he had already shot up the room.

The man was actually firing the gun while police were outside the room ... according to witnesses at the hotel.

Once he was in custody, we're told the gunman was booked for felony possession of a firearm and negligent discharge of the firearm.

Our sources say the weapons was a handgun with an extended magazine.

Luckily, no one was injured at the hotel.

The area will be heavily trafficked by media and celebs leading up to Clive's party Saturday night -- attendees have to pick up credentials ahead of the event.