Robert Downey Jr. mourns loss of longtime assistant, Jimmy Rich: 'He was a brother'

Robert Downey Jr. is mourning the loss of his longtime assistant, Jimmy Rich.

The "Iron Man" star took to Instagram on Thursday to memorialize Rich, who he said died in a car accident Wednesday night.

"This is not news. This is a terrible and shocking tragedy," Downey Jr. began. "He was my brother, my right hand man, an uncle to our kids and beloved by all who experienced his singular character and wit."

The 56-year-old actor continued: "Our thoughts go to his relatives, friends, co-workers, and all the fans who knew him as the man who supported every step of my recovery, life and career."

Downey Jr. ended his post by again sending condolences to Rich's "beautiful family, and the legacy of hope and redemption his life will continue to represent. Peace Be Unto You."

Rich is listed on IMDb as having been Downey Jr.'s assistant since at least the early 2000s and he was with the Hollywood icon for many of his outings in the Marvel Cinematic Universe.

Many of Downey Jr.'s MCU co-stars took to the comments to pay tribute to Rich, including Chris Hemsworth, Mark Ruffalo, Chris Pratt, Jeremy Renner, Josh Brolin, Clark Gregg and Gwyneth Paltrow.

Chris Evans, who played Captain America in the MCU, also posted about Rich's death on Instagram, sending love to Rich's friends and family and asking for fans to show Downey Jr. love during this "incredibly dark time."

"I don't have the words. Jimmy Rich was unlike anyone else. He left an indelible impression on everyone he met. No one more so than my brother @robertdowneyjr," Evans wrote, calling them "inseparable."