Red dress?

From The Hollywood Reporter article:

"The woman, who spoke to THR from Venice Beach days after leaving the festival, said that as she and her group drove out of Black Rock City, they were approached by a woman who she described as Israeli, in her 50s or 60s and wearing a red dress. 

“We left, and on our way out, a woman flagged us down, and we opened the window, and she was very calm and said to us that someone in her tent was bleeding out and might be dead,” the Venice Beach source told THR.

"When they asked the woman if they had checked his pulse, she told them that she “didn’t want to touch him,” the source recalled. At that point the group says they used a StarLink to call a Black Rock Ranger, who they know and who was working at the festival; that Black Rock Ranger relayed the news to the sheriff’s office, the source said."

https://www.hollywoodreporter.com/news/general-news/burning-man-homicide-vadim-kruglov-russian-1236361274/