"The (medical examiner) is telling us it happened before the body had been tossed out in the car seat," said Galveston Police spokesman Lt. Jorge Trevino.
Authorities on Wednesday were still searching for the father, the last person seen with the infant. An Alvin woman, whose name has not been released, has tentatively identified the body as that of her son.
But the infant still was not positively identified after the autopsy.
Investigators were preparing to subpoena footprints from the hospital where the infant was believed to be born in order to positively identify him. But the hospital, which is not mandated to keep such records, might not have the infant's footprint, Trevino said.
"If not, then we will have to depend on DNA testing and that may tie it up for another three or four days even if we expedite it," he said.
The autopsy did not offer additional clues about how exactly the infant was killed or give an exact time of death. He was found Tuesday morning wearing only a diaper in a grassy area near Seawall Boulevard in this island city about 50 miles southeast of Houston.
"We are not closer to knowing what happened," Trevino said. "The (report) didn't tell us a whole lot."
Trevino said investigators have learned that the couple thought to be the infant's parents had been arguing Monday night in their home in Alvin, about 30 miles northwest of Galveston.
"I don't know if there was a history of that," he said.
By the time the child's father left with his son sometime between 5 a.m. and 5:30 a.m. Tuesday to get a car repaired, the couple was no longer arguing, Trevino said. The mother began calling hospitals hours later after becoming concerned about the baby because the father had left with few provisions for the child.
A Galveston couple found the body as they drove slowly along a road looking for wildlife.
There had been initial reports that the infant might have been thrown out of a moving vehicle.
"But the location of the child and the baby seat is not consistent with a moving vehicle," Trevino said. "It was likely the car was stopped."
The infant was in the car seat when it was tossed and the child was apparently thrown out when the seat hit the ground, Trevino said.
The infant's father is being called "a person of interest" in the investigation, police said. A nationwide search is being conducted for the father, who dyed his hair blond before the infant's death.
The discovery of the baby's body comes just three months after a fisherman found the remains of a 2-year-old girl in a plastic box that had washed ashore in Galveston Bay. That child, dubbed "Baby Grace," was later identified as Riley Ann Sawyers of Spring.
Riley's mother and stepfather are charged with capital murder in her beating death.
