UPLAND (CBSLA) — A 25-year-old Upland woman was officially charged Thursday with assaulting her infant daughter to death and attempting to murder her toddler son by dropping him off a balcony.

Tierra Rose Ortega is facing one count of assault on a child causing death in the killing of her 6-month-old daughter Ezlynn, the San Bernardino County district attorney’s office reports. She also faces one count of attempted murder with the allegation of great bodily injury for throwing her 19-month-old son Jerricho off a second-floor landing.

READ MORE: One Killed In Fiery Wreck On 60 Freeway In Hacienda Heights

Ortega plead not guilty Friday morning to the charges when she appeared in San Bernardino County Superior courtroom in Rancho Cucamonga.

Tierra Ortega. (Upland Police Department)

At 11:30 a.m. Tuesday, Upland police responded to a 911 call from an apartment complex in the 600 block of North Wedgewood Avenue on a report that a mother, later identified as Ortega, was holding her son over the side of a second-story landing.

As officers were responding, Ortega let go of the boy and he fell to the ground, police said. When she saw that officers had arrived on scene, she also threw herself head-first off the same landing, police said.

READ MORE: Driver Slams Into Homeless Encampment In Brentwood

Officers then searched Ortega’s apartment, where they found her infant daughter not breathing and with a fractured skull.

Ezlynn Ortega. (Upland PD)

The two children were airlifted to Loma Linda Medical Center, where Ezlynn was pronounced dead, police said. Jerricho suffered a broken foot, but survived and was in stable condition. He was expected to be released from the hospital as soon as Thursday, police said.

Ortega herself was treated at a hospital for facial injuries before being booked into jail.

The children’s father was not at home at the time of the incident. The complex’s property manager told CBS2 the family of four moved in from La Puente about a year ago.

MORE NEWS: Driver Speeds Away After Hitting, Killing Woman On Topanga Roadway