On July 8, 2020, Rivera accidentally drowned while boating with her 5-year-old son Josey Hollis Dorsey in Southern California's Lake Piru. Local investigators believe that while swimming with Josey, their pontoon floated away and Rivera likely died trying to save her son from the water’s strong current. Since the fatal incident, Rivera's estate and her ex-husband Ryan Dorsey have filed a wrongful death lawsuit against Ventura County.
Rivera had already completed her voice work for The Long Halloween, which will be released as a two-part project. Supernatural's Jensen Ackles, who after previously voiced the character of Red Hood/Jason Todd in 2010's Batman: Under the Red Hood, will star as Batman/Bruce Wayne. Other cast members include Josh Duhamel voicing Harvey Dent, Billy Burke as James Gordon, Troy Baker as Joker, and Jack Quaid as Alberto.
The Long Halloween, which ran for 13 issues from 1996-1997, was written by Jeph Loeb and illustrated by Tim Sale. The story takes place early in Batman's career, when the city of Gotham is threatened by a villain named Holiday. These comics are said to have been influential to Christopher Nolan's Dark Knight trilogy and as well as the upcoming Robert Pattinson-led film The Batman.
Rivera's final posthumous TV appearance was in July 2020, when she was a guest judge on an episode of the third season of Netflix's reality baking competition Sugar Rush.
Batman: The Long Halloween, Part One is expected to drop later this spring or summer.