ORLANDO, FLA. -- A man riding in a car with his cousin shot and killed another passenger then returned to the same neighborhood near Orlando hours later and shot four more people, killing a journalist covering the original shooting and a 9-year-old girl, Florida police and witnesses said.

Orange County Sheriff John Mina characterized the shootings Wednesday as random acts of violence. Mina said during a news conference that 19-year-old Keith Melvin Moses has been arrested and charged with first-degree murder in the initial shooting that killed Nathacha Augustin, 38, and that "numerous more charges" would follow.

Spectrum News 13 identified the slain reporter as Dylan Lyons. Photographer Jesse Walden was also wounded. Mina said Walden has been talking to investigators while being treated at a hospital.

The two were in an unmarked news vehicle on Wednesday afternoon covering the first homicide when a man approached and shot them, Mina said. The man then went to a nearby home where he fatally shot T'yonna Major and critically wounded the girl's mother. Officials have not released the mother's name.

Mina said Thursday that investigators do not know the motive for any of the shootings. He said Moses is a known gang member but that the shootings didn't appear to be gang-related. It was not clear if Moses knew that two of the victims were journalists and noted that their vehicle didn't look like a typical news van or have the station's logo on it.

The sheriff said when deputies arrested Moses they seized a Glock semiautomatic weapon that "was still hot to the touch, meaning it had just been fired, and there were no more rounds."

Moses complained he was hurt and was taken to a hospital where he attacked medical staff, Mina said. He has since refused to speak with detectives.

It was not immediately known whether Moses has a lawyer who can speak on his behalf.

A man who called 911 after Augustin was shot told investigators that he was driving around smoking cannabis with her when he spotted Moses walking along a road. He said Moses "seemed down" so he offered him a ride, according to an arrest affidavit. Moses climbed into the backseat, behind Augustin, and about 30 seconds later the driver said he "heard a loud bang" and saw blood on Augustin's face.

He said he stopped and Moses fled. The driver called 911.

He told investigators that Moses and Augustin didn't know each other and that he didn't hear the two exchange any words before the shot was fired.

Mina said Thursday that the driver and Moses are cousins.

Deputies went to the Pine Hills area, just northwest of Orlando, at around 11 a.m. Wednesday after reports that a woman in her 20s had been shot.

About five hours later, 911 calls began coming in from the same scene, the sheriff said. Police found the journalists who had been shot being helped by a news crew from another station, WFTV.

"I want to acknowledge the brave WFTV news crew who was there and witnessed the shooting and rendered aid to the victims until our deputies arrived," Mina said.

Lyons was born and raised in Philadelphia, and graduated from the University of Central Florida, the station said. Before joining Spectrum News, he worked for a station in Gainesville.

"(Lyons) took his job very seriously. He loved his career. He loved what he did," said Spectrum Sports 360 reporter and friend, Josh Miller. "He loved the community, telling the stories of people, reporting on the news, and he was just passionate about what he did."

Rachel Lyons, the reporter's older sister, is via GoFundMe. She wrote that Lyons would have turned 25 in March. He is also survived by his parents and fiancee.

Worldwide, 40 journalists were reported killed last year, plus another two this year before Wednesday, according to the Committee to Protect Journalists. One of those was in the United States.

Jeff German, who covered politics and corruption for the Las Vegas Review-Journal, was found dead outside his home in September after being stabbed multiple times. Former Clark County Public Administrator Robert Telles, who had been a frequent subject of German's reporting, has pleaded not guilty to a murder charge.

In 2015, Virginia reporter Alison Parker and cameraman Adam Ward were shot and killed during their live TV broadcast for CBS affiliate WDBJ7. The suspect, a former reporter for the TV station, died by suicide during the law enforcement search for him.

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Frisaro reported from Fort Lauderdale, Fischer reported from Miami; Associated Press writer Stefanie Dazio in Los Angeles contributed to this report.