A gunman opened fire on two television journalists covering a murder near Orlando, Florida, on Wednesday, killing one and wounding the other.
He also shot a nine-year-old girl and wounded her mother in a nearby home, authorities have said.
The gunman identified as Keith Melvin Moses, 19, was arrested shortly after the shootings on Wednesday, said Orange County Sheriff John Mina.
Mr Moses was also formally charged in connection with the killing of a woman in her 20s hours earlier, a shooting that the two journalists were covering when they came under fire, Mr Mina said.
None of victims, a reporter and a photographer for Spectrum News 13, was identified.
Mr Mina said Mr Moses was armed with a pistol when taken into custody.
He has a lengthy criminal record that included arrests on charges linked to firearms offences aggravated battery, assault with a deadly weapon, burglary and grand theft.
Mr Mina said no motive had been determined, but believed the gunman to have been an acquaintance of the first victim who was shot while sitting in a car with the gunman and another person.
The sheriff said the two newsman became targets because they were journalists. He said their vehicle did not have TV station markings typically seen on a news van.
They were in or near their vehicle when shot.
"As far as we know, he had no connection to the reporters and no connection to the mother or the nine-year old, and we don’t know why [the killer] entered their home," the sheriff said.
He said both the mother and the surviving journalist were in hospital in critical condition.
White House press secretary Karine Jean-Pierre posted a message of condolences on Twitter.
"Our hearts go out to the family of the journalist killed today and the crew member injured in Orange County, Florida, as well as the whole Spectrum News team," she said.