A 23-year-old mother admitted to being high on marijuana the day her 4-year-old son was killed in a house fire in Keizer, Oregon. At a Monday court hearing, prosecutors also revealed that Niya Sosa-Martinez was previously convicted of child neglect in 2012, involving her son Andre and 6-year-old daughter who was at school when their home caught fire on Friday. Sosa-Martinez remained expressionless in court, though she did tear up when she was formally charged with second-degree manslaughter and endangering the welfare of a child. Scroll down for video Tragedy: Niya Sosa-Martinez (left) was charged on Monday with second-degree manslaughter and endangering the welfare of a child after her 4-year-old son Andre (right) was killed in a house fire
@highlight
Niya Sosa-Martinez's son Andre became trapped in their Keizer, Oregon home when it caught fire Friday afternoon
@highlight
The 4-year-old died in the blaze while his 23-year-old mother was able to escape to safety
@highlight
Sosa-Martinez's 6-year-old daughter was at school at the time
@highlight
Prosecutors revealed Monday that Sosa-Martinez had been convicted of child neglect before, in 2012
@highlight
Also told investigators she was high on marijuana at the time of the fire
@highlight
She has been charged with second-degree manslaughter and endangering the welfare of a child and ordered held without bail
Terrible loss: A neighbor described @placeholder as a 'happy little guy'.