A man wearing hospital scrubs threw a toddler 30 feet from a pedestrian overpass onto a major highway Thursday, and the boy was later pronounced dead, authorities said.
A 23-year-old man was arrested after witnesses saw him throwing something, followed him and called police, officials said.
One or two vehicles may have struck the 2 1/2-year-old boy, but it was unclear exactly what killed him, The Honolulu Advertiser reported.
A white sheet covered the body on the westbound lanes of the H-1 freeway, a major route through downtown that police temporarily closed. The scene was just blocks from the Capitol and the governor's mansion.
The man was taken to the Honolulu police station and then to a hospital, said police spokeswoman Michelle Yu. She didn't know whether the man had a history of mental illness or a criminal record.
"That will be part of the investigation," Yu said.
The man screamed "Thank you for everything" to television crews as he was escorted to a cell block.
There were no reports of a missing child, police Capt. Frank Fujii said. Officers were contacting day-care centers and other area facilities to find out where the child came from.
"It's a sad incident. It's something we never wished happened," Fujii told the Honolulu Star-Bulletin.
The suspect was wearing scrubs, with the bottoms cut off as shorts. It wasn't known whether he had come from a hospital, or which one, Fujii said.