Besides lashing out at haters on Twitter, Chris Brown reportedly was trying to shush partygoers while attending Rihanna's 24th birthday soiree at Hearst Mansion club on Monday (Feb. 13). TMZ reports that Breezy tried to keep his attendance under wraps by forcing people at the party to sign confidentiality agreements.

Before entering the venue, the Grammy Award-winning singer sent his bodyguards inside to get signatures from every attendee. Not everyone signed, but eventually Brown went inside to join the party. Brown's reps told TMZ that confidentiality agreements were distributed only to club employees at the party and anyone who was caught videotaping or taking a picture of the singer.

Nevertheless, Brown and Rihanna reportedly sat with each other and held hands. Among the partygoers in attendance included Katy Perry, Coldplay's Chris Martin and Bruno Mars.

The main attraction of the night had to be the birthday cake -- it featured a chocolate-covered replica of RiRi straddling a joint made out of white icing. Obviously, the cake was made in jest of Rihanna being photographed smoking a spliff why vacationing in Hawaii in January.

Rihanna's 24th birthday isn't until Feb. 20 but the Barbadian songbird is getting a jump start on the celebration. More than 20 bottles of Armand de Brignac Brut Gold Champagne was popped during Monday's festivities, and Luxe cigars by Camacho were handed out as party favors.