Nicole Richie Mourns Friend Casey Johnson

For the second time in less than six months, one of Nicole Richie's friends has died of a drug overdose.

Casey Johnson, heiress to the Johnson & Johnson family fortune and a regular fixture on the New York and Los Angeles social scenes, was confirmed dead on Jan 4, days after dying alone in her home. The troubled young mother sent her last Twitter message at 1:12 a.m. on Dec. 29, saying, "Sweet dreams. I'm getting a new car."Seven days later, a maid arrived to find Casey's body. Johnson was 30-years-old.

Richie and Johnson grew up in the same circles, and ironically enough, her death brought Richie back together with another one of her childhood friends, Paris Hilton. Paris's sister Nicky gathered several of Johnson's friends, including Richie, at her house. “Been a sad day. But my sister made it better by having all of Casey’s close friends come over to her house today to be together,” Paris tweeted. “It was nice to get together and share our feelings and memories of our dear friend," she continued. "We celebrated her life, we all miss and love her so much.”

Johnson had recently made headlines for her erratic behavior and engagement to Tila Tequila. Her death comes not long after Richie's ex-fiance DJ AM (aka Adam Goldstein) was found dead of an overdose on Aug. 28, 2009.