Ebony Wilkerson, 32, drove her vehicle into the ocean at Daytona Beach on Tuesday evening, prompting several people to chase after and pull the woman and children to safety.
The dramatic rescue was all caught on video.
Rescuers at the time said the children inside the vehicle were screaming that their mother was trying to kill them.
"The kids are like, 'No there's a baby. There's a baby,'" said Tim Tesseneer, one of the rescuers. "She (the mother) wouldn't say a word. She didn't tell us nothing about a baby. She had this look on her face. I can't describe it. It was just an awful blank look, like spaced out look."
Now police are saying they conducted a welfare check on Wilkerson just hours before she drove her van into the ocean. Wilkerson's sister said the woman had been talking about demons being in the house.
At the time of the check, Volusia County Sheriff's officials said her behavior wasn't unusual.
"If she made any statements that she was suicidal or homicidal officers would have taken her into custody," said Volusia County Sheriff Ben Johnson.
Johnson said Wilkerson was afraid her ex-husband would hurt her or her children.
Florida Department of Children and Families took custody of the three children, ages 3, 9 and 10.
[WESH-TV, Orlando, Fla.]