(CNN) -- A man believed to have shot six people, one of them -- his father -- fatally, before turning the gun on himself knew all the victims, authorities said Tuesday. But they stopped short of saying the victims were targeted.
Clifford Miller Jr. died from a self-inflicted gunshot wound after the shootings Monday in and around Gainesville, Florida, police said. Police Chief Tony Jones said the incidents constituted a "tragic day for Gainesville."
Miller, 24, lived with his father, Clifford Miller Sr., who died, authorities said. The remaining victims were hospitalized with their conditions ranging from fair to critical.
It was believed Miller fired all the shots from his vehicle, said Gainesville police Cpl. Tscharna Senn. "We firmly believe that he acted alone in this incident," she said. Miller is believed to have driven to each of the victims' locations and shot at them with a revolver.
Miller had "a relationship" with all the victims, she said, but would not elaborate. "Right now, we do not have a motive," she said. "We're not prepared to say any of these victims were targeted."
The investigation was ongoing, she said.
The first shooting was reported about 4 p.m. Monday, and other reports followed. Between 4:03 and 4:25 p.m., a total of 25 emergency calls were received, authorities said.
Miller had a long criminal history that included arrests for cocaine possession and driving under the influence, Senn said. In March of this year, he was found mentally unable to stand trial.
Gainesville, located in north-central Florida, is home to the University of Florida, but the shootings appeared to be unconnected to the school.
CNN's Vivian Kuo contributed to this report.