The head of Colorado’s prison system was shot dead as he opened his door on Tuesday night, according to police.

Police don’t have any descriptions of the shooter. They’re not even sure if the suspect left on foot or drove away in a vehicle.

What they do know is that an empty, boxy-shaped black car -- possibly a 1990s model Lincoln -- had been seen with its engine running on the street where Tom Clements lived. That same car was seen driving away later in the night.

While authorities weren’t aware of any threats made against Clements, they say that his position within the prison system may have made him a target.

Colorado's Gov. John Hickenlooper, who has ordered all flags to be lowered to half-staff, described Clements as a "dedicated, committed, funny, caring expert at corrections" who tried to ensure that prisoners had adequate support before their release.

"In many ways, he helped define what a public servant is," Hickenlooper said. "He did his job quietly and intently."

Clements, 58, had worked in corrections for more than three decades. He was appointed as the executive director of Colorado’s prison system in January 2011.

Clements leaves behind a wife, Lisa, and two daughters.

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