A man suspected of killing a woman on Wednesday in Florida returned to the scene of the crime hours later and gunned down a television reporter and a nine-year-old girl, authorities said.

Orange County Sheriff John Mina said that a 19-year-old man, Keith Melvin Moses, had been taken into custody and was believed responsible for the shootings.

The attacks occurred in Pine Hills, a suburb west of Orlando in central Florida. A 20-year-old woman was slain there at around 11am, the sheriff's department said Wednesday. 

A team from Spectrum News 13 arrived hours later to cover the murder, Mina said at an evening news conference. 

Shortly after 4pm time, Moses arrived and opened fire on a Spectrum camera operator and a reporter as they stood near their vehicle, killing the reporter and wounding the camera operator, the sheriff added.

The gunman then entered a nearby home and shot a woman and her nine-year-old daughter.

The victims were all taken to the hospital, but the girl and the Spectrum News 13 reporter died, Mina said.

"We have detained the person believed to be responsible for the murder this morning, as well as the shootings this afternoon," Mina said.

He added that the suspect had a "lengthy criminal history" that included "gun charges, aggravated battery and assault with a deadly weapon, burglary and grand theft charges."

The detainee, who knew the woman killed in the morning, had no ties to the other victims, the sheriff said. 

None of those shot were immediately identified.

"No one in our community, not a mother, not a nine-year-old child, and certainly not news professionals should become victims of gun violence," Mina said.