(CNN) Authorities in California had a stern warning for whoever abducted a 3-week-old girl who was later found dead in a strip mall dumpster: "Our police officers will do everything in their power to find you."

On Sunday, police said San Diego authorities had found her body.

The San Diego Coroner's Office confirmed the deceased infant was Eliza.

"Eliza's life was just beginning and it was quickly taken away and all due to a senseless act of violence," Long Beach Mayor Robert Garcia said Monday. "To the person or persons that are responsible ... please know that our police officers will do everything in their power to find you."

Long Beach Police Chief Robert Luna repeatedly urged anyone who may have witnessed the crime to come forward, saying the public's help will be "extremely critical to solving this case."

The abduction and death of the infant has shocked the community, including police officers accustomed to seeing tragedies.

"There is nothing as horrendous as a child, a baby ... being taken from her home and then being left in a trash dumpster," said Luna, who repeatedly called the person responsible a coward.

Authorities told CNN that the attacker may have known the family.

Meanwhile, two of the shooting victims remain in critical condition at an area hospital, police said, and a third has been treated and released.