A 2-year-old is dead and his mother's boyfriend is behind bars. Neighbors say that mother should've known she was welcoming a potential danger into the household.That's because 35-year-old Cory Simmons is a registered sex offender in the state of Illinois. A simple search reveals he was convicted of criminal sex abuse of a teenage victim in 2008.Documents say the toddler's mother met Simmons on an online dating site and he moved from Illinois to live in the family's house this past January.Simmons is now accused of abusing the child to death while he was babysitting on Feb. 16.Neighbors on Rose Tree Lane question why he was ever left alone with the toddler and his two sisters."If you're a single mom and you're going to go as far as let someone live in your home with your children, know them. Look them up on the internet," said neighbor Amy Brown.Records also show Simmons was arrested for murder in 2003. Those charges were eventually dropped."When I found out about this, I went to my girls and said, this is why mommy doesn't let you play outside, because scary people look just like everybody else," added neighbor Amy Brown.According to an arrest report, the mother of Orlando Morris Jr. left Simmons alone with her kids to go to work.It was during that time that documents say Simmons put his right hand on her 2-year-old son's throat. He reportedly pressed down for two to three minutes.When he removed his hand, the child's arms were reportedly jerking. He then threw up and eventually stopped breathing."It's hideous. It's horrible. The mom should've been protecting her child more," said neighbor Tasha Kilburn.Simmons reportedly asked a detective on scene to "shoot him" and repeatedly requested for the death penalty.Documents allege that investigators found a purple dildo inside the toddler's crib.Police say he denied touching Morris or the other children in a sexual manner.Two sisters of Orlando Morris were taken in by Child Protective Services.Simmons is due in court on Wednesday and faces a felony charge of murder by child abuse.