Ventura County Sheriff Bill Ayub says investigators believe Naya Rivera spent her final moments saving her son's life at the expense of her own.

Naya Rivera, Lake Piru, MissingKevin Winter / Getty Images

"We know from speaking with her son, that he and Naya swam in the lake together at some point during their journey. It was during that time that her son described being helped into the boat by Naya, who boosted him onto the deck from behind," the sheriff said. "He told investigators that he looked back and saw her disappear under the surface of the water."

"The idea perhaps being that the boat started drifting, it was unanchored, and that she mustered enough energy to get her son back onto the boat, but not enough to save herself," Ayub said.

The sheriff also confirmed that there is no evidence of foul play or suicide.

After an extensive search, Rivera's body was found Monday, five days after her disappearance at Lake Piru in Ventura County, California.

"Based on the location that the body was found, physical characteristics of the body, clothing found on the body, and physical condition of the body, as well as the absence of any other persons reported missing in the area, we are confident that the body we found is that of Naya Rivera," Ayub said.