The shootings happened before midnight at the Texas Department of Health and Human Services building in Laredo.
Laredo police investigator Joe Baeza says 12-year-old Ramie Grimmer and her 10-year-old brother, Timothy Grimmer, remain in "very critical" condition at University Hospital in San Antonio.
Baeza said their mother, 38-year-old Rachelle Grimmer, had been unable to qualify for food stamps and pulled a gun in a state welfare office and staged a seven-hour standoff with police that ended with the shootings.
State welfare spokeswoman Stephanie Goodman says Grimmer first applied for food stamps in July but was denied because she didn't supply enough information.
