"You could tell she loved being a mom," a source close to Naya Rivera, who died at age 33, tells PEOPLE

While Naya Rivera's career was a priority, family and motherhood topped all.

"You could tell she loved being a mom," a source close to Rivera, whose body was found Monday after a five-day search on Lake Piru in California, tells PEOPLE in this week's issue. "She was always so sweet."

"Back in the day, her life was all about her career," says another source close to Rivera during her time on Glee. "It was all about acting, singing, using her platform for equal rights, empowerment and anti-bullying."

"But her priorities shifted. She was working less not because she didn't want to work, but because her son came first," the latter insider shares.

Naya Rivera; Josey Hollis Dorsey
Naya Rivera and son Josey
| Credit: CHRIS DELMAS/AFP via Getty Images

In November, Rivera opened up about her 4½-year-old son Josey Hollis, whom she shares with ex-husband Ryan Dorsey.

"I enjoy every minute of it," Rivera previously told PEOPLE at the Women's Guild Cedars-Sinai Annual Luncheon last year. "He is my best friend. I think that juggling work and being a mom, even if you are single or not, is always really challenging, but I cannot complain."

The former Glee star's body was found five days after she went missing during a boating trip in Ventura County, California, with Josey.

At a news conference Monday afternoon, Ventura County Sheriff Bill Ayub recounted what Josey told authorities about the tragic accident at Lake Piru.

"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," Ayub added.

Naya Rivera
Naya Rivera
| Credit: Amy Sussman/Getty Images

Ayub said that "there are a lot of currents on the lake that appear particularly in the afternoon" and that authorities believe she disappeared in the "mid-afternoon."

"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 added that there is no evidence of foul play or suicide. An autopsy will be performed at the Ventura County Medical Examiner's Office, and the actress will be officially identified based on dental records.

Rivera was 33 at the time of her death.

Glee cast
Glee cast at Lake Piru
| Credit: Al Seib/Los Angeles Times/Getty

During the news conference, Ayub expressed his condolences to Rivera's loved ones during this heartbreaking time.

"As you can imagine, it has been an extremely difficult time for her family throughout this ordeal. As fathers, mothers, sons and daughters, our hearts are with them and we share in their grief for Naya's loss," he said. "We have been in direct contact with the family throughout this entire time, and we've kept them updated on the progress of our search efforts throughout."

"Our hearts also go out to Naya's many friends and fans, who have been holding out hope for the best over the last few days," Ayub added.

For more on Naya Rivera, pick up the latest issue of PEOPLE, on newsstands Friday.