BELLEVILLE, Ill. — An Illinois woman accused of gunning down two of her children was denied bail and granted a public defender Friday before being led in shackles back to the jail and isolated confinement under suicide watch.

Yokeia Smith faces two counts of first-degree murder. Associate St. Clair County Judge Julie Katz entered a not guilty plea on the 25-year-old’s behalf during Friday’s brief arraignment. A day earlier, the single mother of three agreed to be returned to Illinois from St. Louis, where she was arrested shortly after the Aug. 31 killings.

Authorities say Smith killed her 5-year-old son and 4-year-old daughter with close-range shotgun blasts to the head in their East St. Louis apartment. Smith’s 8-year-old son escaped unharmed and is in the custody of relatives.

Investigators have offered no details about what may have motivated the killings.

Smith’s relatives have publicly pledged their support for her, saying she was bipolar and on anti-depression medication. Smith’s lengthy criminal background includes a litany of traffic offenses and various instances of assault and battery, most of them misdemeanors that authorities have suggested were not indicators that Smith’s legal troubles would escalate to murder.