A 5-year-old Florida girl was likely alive when her father dropped her 62 feet off a bridge into the choppy waters of Tampa Bay, St. Petersburg police said.

Phoebe Jonchuck, a kindergarten student, was found in the water about an hour and a half later and pronounced dead at a hospital early on Thursday. Her father, 25-year-old John Jonchuck, has been charged with murder.

"Based on preliminary evidence, our investigators believe Phoebe was alive when Jonchuck dropped her from the bridge," St. Petersburg Police said in a statement.

An off-duty police officer thought he heard her scream as he witnessed the father remove the girl from a vehicle and throw her over the bridge railing early on Thursday, police said.

John Jonchuck was questioned by authorities just hours before the overnight incident following reports of his bizarre behavior. He assured them that he had no plans to harm himself or anyone else.

Phoebe Jonchuck's family was well-known to child welfare officials at the Florida Department of Children and Families, which had received multiple reports alleging domestic violence, drug abuse and mental health concerns involving both of her parents.

On Wednesday afternoon, the department received a call to its abuse hotline concerning the mental state of John Jonchuck, who had custody of his daughter, according to agency records.

"The father seems depressed and delusional, but does not appear to be under the influence of any substances," according to the report.

In the wake of Phoebe Jonchuck's death, the agency said it would change its hotline criteria to require investigators to visit within four hours when a caregiver appeared to be suffering a psychotic episode.

Deputies with the Hillsborough County Sheriff's Office had found no grounds to detain Jonchuck on Wednesday afternoon.

They questioned him about reports that he called an attorney "God" and asked her to translate a Bible that was written in Swedish, according to a police report.

Jonchuck told them "God had spoken to him and gave him newfound clarity in his life," the report noted.

St. Petersburg police said they want to speak with any clergy who Jonchuck contacted before his daughter's death.

Jonchuck remains in jail without bail, facing charges of first-degree murder, aggravated fleeing and eluding, and aggravated assault with a deadly weapon on a law enforcement officer.