By Ann Rubin
St. Louis (KSDK) - A toddler is in critical condition tonight and St. Louis police want to know how she was injured.
Now they're questioning her mother's boyfriend.
"The baby was not responsive at all. Not moving nothing," said neighbor Suzanne Bell.
The little girl, just 20-months-old, was immediately put on oxygen and rushed into a waiting ambulance.
Authorities say she had been left in the care of her mother's 24-year-old boyfriend. He told them she fell off the bed.
Doctors aren't so sure. The child is in critical condition with injuries to the brain, liver and ribs.
Neighbors believe the mother trusted the wrong person.
"It's unfortunate that she had to work and go to school and she just thought she could trust him. And he's just a boyfriend that just wasn't worthy," said Bell.
Rachel Crowe with the St. Louis Crisis Nursery says, before making a decision about who to trust with your kids, parents need to ask the right questions.
"Not everybody that you're acquainted with or that you have a relationship with is a safe person to leave your child with," said Crowe. "So the first thing is, are they used to being around children? Are they used to being alone with children?
She added, "Are they used to that pace? If they're not, they're probably not the safest person to leave your child with."
St. Louis police responded to the home on North 20th, taking the boyfriend in for questioning.
Investigators are still trying to determine whether what happened inside, rises to the level of abuse.
Those that know the family say this never should have happened.
"I mean a helpless child. Why? It's sad. Very sad," said Bell.
The St. Louis Crisis Nursery has a 24-hour helpline available for parents: 314-768-3201.
St. Louis police continue to investigate this case.