In November 2020, Rivera's ex-husband, Ryan Dorsey, and estate brought wrongful death lawsuits against Ventura County and the management of Lake Piru.

Lake Piru is a man-made reservoir in the Los Padres National Forest in Ventura County, California, and is sourced by the Santa Clara River.

[2] The Lake Piru Recreation Area was closed to the public for much of 2020, with the closure starting before April 4[3] because of the COVID-19 pandemic and lasting until it reopened on July 1.

In a 2017 interview, Rivera had mentioned a scary experience on one such trip, when the anchor of her family's boat got stuck and her father injured himself on the propeller trying to free it.

[7] The boat had begun to drift and rock violently while they were in the water because of the wind, which Ryan Dorsey's lawsuit says reached speeds of up to 21 mph (34 km/h) that afternoon.

[17][19][20] After Dorsey was found at about 5:00 p.m. on July 8, 2020, in the Narrows, an area at the north of the lake that can be quite deep and windy,[21] a 9-1-1 call was made and a formal search and rescue operation was launched.

[37] On July 14, the Ventura County medical examiner released an autopsy report stating that the cause of death was an accidental drowning and that there was no evidence of injury or intoxication.

[7][39] Fans of Rivera posted messages of support during the time of her disappearance,[40] though some expressed "frustration" on social media as the sheriff's office repeatedly asked fans not to attempt to search themselves in the land around the shore of Lake Piru; while Morris had initially suggested she would do this, she also joined the authorities in asking civilians to keep away, as they may get into difficulty in the rural terrain and need rescuing themselves.

[41] Shortly after Rivera's disappearance was reported, a petition was started by fans to have signs warning of the danger of swimming erected at Lake Piru.

In May and June 2020, Michele had been the subject of backlash as many of her co-stars accused her of unpleasant and even racist behavior on set, and she had been absent on social media after this.

[43] In previous years, Rivera had personally spoken out against Michele, saying she was difficult and that they were not on speaking terms by the end of the show's run, but said that they did not have any "beef".

[14][48] The suit claims that there were no signs to warn of the dangers of the lake and of swimming in the lake, and that the rental boat provided to Rivera did not meet safety standards under California law, specifically that it did not come equipped with flotation devices, nor "with a safely accessible ladder, adequate rope, an anchor, a radio, or any security mechanisms to prevent swimmers from being separated from their boats".

[48] The lawsuit is also pursuing survivor's claims for Dorsey and claims of negligent emotional distress,[49][50] stating that "Rivera may not have known that her son had made it to the boat but she surely knew that she was dying and would not make it back to her son",[13] as well as highlighting the later publication of toxicology reports, which it says were the defendants' "attempts to discredit [Rivera] in the media and distract from their own negligence".

[53] Insider listed a photograph of Glee cast members holding hands along the shore of Lake Piru on July 13 as one of the most powerful images of 2020.

[57] Other reactions from public figures included prominent politicians Alexandria Ocasio-Cortez and Kamala Harris, who noted her profound impact in creating intersectional representation on primetime television;[58][59] Demi Lovato, who played the girlfriend of Rivera's character on Glee in its fifth season, expressed similar sentiments, writing: "The character you played was groundbreaking for tons of closeted (at the time) queer girls like me and your ambition and accomplishments were inspiring to Latina women all over the world".

[61][62][63] Rivera's many Glee co-stars, a group of whom had gathered at the lake on July 13 to say prayers shortly before her body was found,[64] also paid tribute.

[66][67][61] The show's creators, Ryan Murphy, Ian Brennan, and Brad Falchuk, announced that they planned to start a college fund for Rivera's son, Josey.

[70] The media noted that Rivera's body was found on the anniversary of the death of her co-star and friend, Cory Monteith seven years earlier;[15][71] a tribute she had sung for him, the song "If I Die Young", saw a surge of views.

[75][76] Another member of the cast, Kevin McHale, tweeted that "[he is] not religious by any means, but you'd be hard-pressed to convince [him] that Cory didn't help find our girl [Rivera] today".

[77] Monteith's mother, Ann McGregor, also posted a lengthy tribute, writing how much Rivera's friendship had meant to her son and their family and saying: "We'll carry you in our hearts forever.

[84] In February 2020, shortly before filming was shut down, Rivera recorded a guest spot in an episode of the Netflix show Sugar Rush, to be released on July 31, 2020.

[89] In late July 2020, Filipino director Drama Del Rosario thanked Rivera and her representation in his acceptance speech for the Jury Prize at the PBS Short Film Festival; his winning film looked at how his family came to accept his sexuality when he was outed in high school, with Rivera's Glee character Santana Lopez helping them understand, and he said "[she] is a testament to how much queer entertainment can change the life of a family on the other side of the world".