The circumstances of the fatal shooting of a woman while talking to a 911 operator to report being chased on a Phoenix freeway don't point to random violence or a traffic dispute, police said Thursday as they appealed to the public for information.

Detectives determined that Dinya Farmer, 49, reported Wednesday night that she was followed for about four miles of city streets before getting on Interstate 10 and then the State Route 51 freeway, said Sgt. Jonathan Howard, a police department spokesman.

"This increases the likelihood that the crime may be related to some pre-incident contact that has yet to be determined and lowers the likelihood that it was random violence or traffic altercation related," Howard said in a statement.

Howard earlier said that Farmer's 911 call was among a handful from people who reported a white work truck driving aggressively on I-10. The truck was described as having a ladder rack and a tool box. Its occupants were described only as three Hispanic males.

Farmer died at a hospital after she crashed in the freeway median as a 911 operator heard shots fired and the call ended, Howard said. He said he didn't have specifics on Farmer's gunshot injuries.

There was no indication the incident is related to either a 2015 series of shootings on Phoenix freeways or a 2016 series of shootings largely on or near residential streets, Howard said.

Farmer reported being followed from the area of South Seventh Avenue and West Broadway Road. Police hope somebody in that area of south Phoenix can provide information about the suspect vehicle, Howard said. "We're looking for that kind of tip that narrows it down a little bit," he said.

There are many white work trucks, and police in fact found and stopped several near the shooting scene Wednesday night, but none panned out, Howard said.

Police also hope to hear from people whose dashcams might have recorded part of the incident or who noticed the white truck driving erratically or aggressively, Howard said. "If somebody has a photographic memory and remembers the license plate number, we need that person to call us," he said.

The early evening shooting closed part of the SR 51 freeway in central Phoenix overnight as police investigated. The highway was reopened before the start of the Friday morning commute.