September had been a month of celebrating Bertha Mendoza’s birthday, as well as her son's and grandson's.

It's now also the month she died.

Mendoza, 56, was one of the employees of Impact Plastics Inc. in Erwin, Tennessee, who were swept from the open bed of a truck trying to bring her and other workers to safety from the floodwaters of Hurricane Helene.

Her birthday was Sept. 2. But unlike other years when she and her son Guillermo, 33, marked their September birthdays individually, she had asked to have a family gathering to celebrate them all.

“We just decided to throw a big birthday party on Saturday," Sept. 21, Guillermo Mendoza said in a phone interview. “That was amazing. We got to see everybody there. That was a good time for my mom.”

They even had some one of her well-regarded tres leches cakes, the delicious and beautifully decorated dessert that people in town would request. She made it for people not as a business, but because she enjoyed it and had a passion for it, her son said.

Bertha was proud of her four children: Emanuel Ibarra, Guillermo Mendoza, Clarissa Flores and Esteban Mendoza.

Her husband of 38 years, Elías Mendoza, had been a seasonal agricultural worker in the United States. After Bertha tired of the family separations while he worked the fields, he applied for green cards and brought her and his children to the U.S. in 1998. They settled in Erwin.

“She was the healer of the family. She was the backbone of the family. She would be the one that would pretty much bring the family together for celebrations, for birthdays," Guillermo said, adding that in hard times, "one would find counsel in her."

Bertha was originally from Guanajuato, a small town in the state of Michoacán in Mexico. Her grandmother and mother are there.

She attended Centro Cristiano Siempre Gozosos in Johnson City, Tennessee, the same church her children went to growing up.

She was a doting grandmother. “The one thing about my mom is she loved her grandchildren. She loved my two sons and my daughter,” Guillermo said.

Six days after the birthday celebration, on the morning of Sept. 27, Guillermo said Bertha had called him urging him not to go out in the storm and not to take her grandchildren out. She was calm at that time.

Later she called her eldest son to tell him things were getting bad and she wasn’t really sure how she was going to get out of the plant. The next call was to her daughter. Bertha told her that it would probably be their last conversation and that she loved her, Guillermo said.

“Then she called my dad and the rest of the time was with my dad, and she said ‘I love you’ and ‘Please tell my children I love them’ and those were her last words,” Guillermo said.

Guillermo said he grabbed his children’s life jackets, a giant water bottle that sits atop a dispenser, “anything that would be floating, anything,” and headed to her. But the water was too high and he couldn’t get close enough.

Family members made urgent calls to 911 in town and in nearby Johnson City.

Authorities said that three people are dead and 10 are missing after flooding from Hurricane Helene submerged the eastern part of the state.

Some other workers who survived have said their supervisors at the plant should have let workers leave much earlier, or never should have had them work that day in the first place. The company has said it released people in time to leave the plant but some stayed behind for unknown reasons. A state investigation is underway.

Guillermo wasn’t ready to discuss who should be held accountable.

"I’m not sure exactly how to feel. At first it was anger, then sadness. Now I feel at peace, at least knowing my mom is resting in peace, in a far better place,” said Guillermo, a minister at the First Baptist Church of Erwin. “She would want to see us again, and she would want to not compromise our beliefs.”

He said his mom touched a lot of lives.

“If you just spoke to her a couple of minutes, you felt like she was your mom," Guillermo said. "She loved people. She cared for people.”

When he spoke to NBC News, he was at the funeral home planning his mom's services.

“Right now, just the next couple days,” Guillermo said, “our full energy is laying mom to rest.”