Colorado beefed up security at the governor's office and other statewide locations amid the search for the person who gunned down the state's prison chief at his home less than 48 hours earlier, law enforcement said.
Tom Clements was shot dead Tuesday night after opening the door at his home in Monument, about 50 miles south of Denver
"We are looking at all potential tips, leads, threats that Mr. Clements may have had from anybody in that prison system," El Paso County Undersheriff Paula Presley told CNN on Thursday. "The investigation is wide open at this point."
Asked whether the 58-year-old's killing might have been a professional hit, Presley replied, "We don't have any specific information that would lead us to that."
Clements was appointed to his job by Colorado Gov. John Hickenlooper, who signed landmark gun control bills Wednesday. Hickenlooper said that Clements was "supportive but not particularly active" in the measures, and there is no indication now if the new laws and his death are related.
Investigators are asking any witnesses to share information about a black, boxy-shaped vehicle that was seen with its engine running but no one inside on Clements' street, Colonial Park Drive, around the time of the shooting.
Several witnesses told authorities they saw the vehicle. Presley said it might be a Lincoln Continental or a Cadillac two-door.
Presley added a new detail about that clue: A man was seen driving the vehicle away from the neighborhood a short time later.
Investigators are scouring databases to try to determine exactly what kind of car they're searching for, she said.
Clements' death shook Hickenlooper, who spoke at an emotional news conference Wednesday.
He repeatedly praised the corrections chief, calling Clements a "dedicated, committed, funny, caring expert at corrections" who tried to ensure that prisoners had adequate support before their release.
"In many ways, Clements helped define what a public servant is," the governor said. "He did his job quietly and intently."
Clements became chief of the state's prison system in January 2011, according to Clements' online state biography. Before that he worked for 31 years in the Missouri Department of Corrections, where since October 2007 he had been director of adult institutions for the department, overseeing 21 adult prisons, the biography says.
-- CNN's Jim Spellman contributed to this report.
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