A prominent reptile expert was killed this week when a semi-trailer slammed into him when he walked onto the roadway, authorities said.

Joseph Mitchell, 71, died Tuesday after being hit by a big rig as he walked onto US 441 in High Springs.

Florida Highway Patrol officials said Mitchell walked into the northbound lanes of the roadway for unknown reasons before he was clipped by the left side of the semi, the Gainesville Sun reports.

Construction workers told WGFL that it appeared Mitchell was trying to pick something up just before the fatal accident.

An investigation into the crash is ongoing, but alcohol was not a factor, according to the Citrus County Chronicle.

The driver of the semi-trailer, Parker Le Meur, 22, of Homosassa, was not charged in the incident.

Mitchell, of Fort White, worked as a herpetology research associate at the Florida Museum of Natural History in Gainesville. He also published or edited more than 500 papers on turtles, according to the Gainesville Sun.

“He was well-known in conservation biology and turtle biology,” the museum’s courtesy assistant curator, Ken Dodd, told the newspaper. “He was easy-going, gentle, very knowledgeable and he cared a lot about all his colleagues.”

News of Mitchell’s death caused a worldwide listserve group among tortoise and freshwater turtle specialists to go “bonkers with tributes to him,” Dodd said.