Karla Alvarado shared a photo showing little Alexia Rose Echeverria.
The baby's body was found behind a dumpster on Monday. She was in a car seat, partially covered by a blanket.
Exactly where and how her life ended remains a mystery, as is the whereabouts of her father, 22-year-old Sacramento County man Alexander Echeverria, with whom she was last seen.
Alexia's mother said she saw Alexander and her daughter on a FaceTime video chat early Sunday. Then, later that day, she received a disturbing phone call.
"At around 4 p.m., he called me crying hysterically," Alvarado shared. "He couldn't even talk, and I was super scared. I was like, 'What's going on? Did something happen to Alexia, did you get into a car accident? What happened?' Because there was a lot of noise in the background, and he couldn't tell me. He just kept crying and crying and crying, and I was like, 'What happened?'"
The case was turned over to the Sacramento County Sheriff's Department, which described the father as a person of interest in his daughter's death.
According to Sheriff's investigators, the father and child were last seen Friday evening in Bellflower as Alexander Echeverria was driving a gray 2014 Volkswagen Jetta.
Authorities said Alexander has family in the Bellflower area.
He is described by authorities as "at-risk" because his family says he suffers from depression.