"She hopefully knows that her sister is watching over her," their mother, Erika Alvarado, told KTLA

A 17-month-old girl died after drowning in her family’s swimming pool on April 29, while her twin sister continues to fight for her life.

CAL FIRE/Riverside County Fire responded to the scene in Moreno Valley, California, and upon arrival firefighters located the two girls, the Riverside Sheriff’s Department confirmed to PEOPLE. The children were then transported in serious condition to local hospitals by ground ambulance.

The Sheriff’s department told PEOPLE they are currently investigating the incident.

Credit: GoFundMe

The parents of toddler Maya, who died, and her sister Makayla, who is in critical condition, told KTLA that they have barely slept since the accident.

“We’re not able to fully grieve because we have to be strong for Makayla. She’s here and she’s fighting,” their father, Jeremiah Edwards, told the news outlet.

The tragedy happened just moments after Edwards and the girls’ mother, Erika Alvarado, fell asleep for a few minutes while the toddlers were playing in the living room, the outlet reported. When Alvarado woke up, she saw that the twins were gone.

Alvarado told KTLA that the home’s doors were locked, but the little girls were able to get out “through a breeze window and pushed the screen off in our home and only the doors were alarmed,” according to a since-changed GoFundMe page description.

Maya and Makayla with their parents Erika Alvarado and Jeremiah Edwards

The twins both fell into their backyard pool, which was not fenced in.

Alvarado told KTLA that she jumped in the water, grabbed Maya and worked on reviving her while Edwards saw Makayla in the pool’s shallow end.

Both daughters had extensive brain damage and were medically sedated after being brought to the emergency room, Alvarado added.

According to KESQ, Maya died on May 12 — the same day that Makayla woke up.

Rafael Victorio, a member of the Moreno Valley Police Department, told KESQ that he was the first to arrive at the scene.

“As I arrived I ran to the backyard. I assumed that the children were in the backyard,” he said. “They were not. I heard someone screaming from inside the house.”

When he walked in, he saw the girls on the floor.

“I just right away just went to the child and said real quick ‘God be with these babies’ and started CPR.”

Alvarado told KTLA that Makayla is staying strong because of her sister.

“That twin connection that people tell us about — she’s thriving off of that,” she told KTLA. “She hopefully knows that her sister is watching over her.”