This Is the Last Known Footage of Naya Rivera

Authorities have released footage of what are thought to be some of Naya Rivera's final moments. A security video shared Thursday shows two people—presumed to be the 33-year-old actress and her 4-year-old son—exiting a vehicle at Lake Piru in California's Los Padres National Forest around 1pm Wednesday, then departing a marina in a rented pontoon boat, reports Today. Rivera was reported missing three hours later. In a 911 call, also released Thursday, an employee of the boat company describes "a little girl in one of the boats by herself," adding "the mom's nowhere to be found." It was actually Rivera's son, Josey Hollis Dorsey, who was found. "He gave enough information to investigators to conclude that his mother never made it out of the water" after the pair went swimming, says Sgt. Kevin Donoghue of the Ventura County Sheriff's Office.

The boy was found asleep on the boat in his life jacket. An adult life jacket was on board. Police therefore presume Rivera drowned. If confirmed, she would be the ninth drowning victim at Lake Piru since 1994, per TMZ. Nearly 20,000 people have signed a petition asking that warning signs be posted for swimmers, who may be unaware that the manmade reservoir has rip currents and a bottom packed with trees and other debris. "Locals of Ventura County don't go to Lake Piru for this reason! Tourists have no idea what they're getting into," the petition reads. Authorities say Rivera had visited the lake before. Despite limited visibility, "we're gonna do everything that we can to find her," Donoghue says. A diver tells CBS News that "there's a lot of shrubbery and sticks that we have to break through as we're going through, so it's kind of a Braille search." (More Naya rivera stories.)