MONUMENT — The head of Colorado prisons was shot to death as he answered the front door of his Monument home, triggering a massive murder investigation and prompting extraordinary safety precautions around the state in case the killer targets other government officials.

Tom Clements, 58, executive director of the Colorado Department of Corrections, died Tuesday night at his home on the 17400 block of Colonial Park Drive.

His wife, Lisa, told a 911 dispatcher that someone rang the doorbell and then shot her husband in the chest, according to a dispatcher’s recording that described her as “very distraught.” The call came in at 8:42 p.m.

Within minutes, deputies found Clements and his wife inside the home on a set of stairs. Medical crews started performing CPR on Clements while deputies worked to secure the area and search for a suspect.

Clements is survived by his wife and two adult daughters, Rachel and Sara.

“Our family has lost a devoted husband and a beloved father,” Clements’ family wrote in a media release. “There are no words at this time to describe our grief and loss. We thank our friends and those praying for us here and across the nation. Your well-wishes and prayers bring us strength.”

Scores of sheriff’s deputies and investigators from state, local and federal agencies investigated through Wednesday at Clements’ home in an upscale, wooded neighborhood east of Interstate 25. The two-story home was cordoned off, and deputies used dogs to search the area.

“We have no known suspect at this time,” said Lt. Jeff Kramer, spokesman for the El Paso County Sheriff’s office.

It does not appear that robbery was a motive for the shooting, Kramer said. Despite Clements’ prominent position, authorities have not ruled out the possibility of a random shooting, he added.

“There is no evidence of a home invasion,” he said.

Gov. John Hickenlooper and others praised Clements for innovations that helped decrease Colorado’s recidivism rate and dramatically reduced the number of inmates in segregation.

But not all of Clements’ changes have been popular among the rank-and-file. Two prisons closed under Clements’ watch, and he would soon have been involved in deciding which other prisons to close in response to a dwindling prison population.

“We know of his position and realize that it is a possible motive for a crime such as this,” Kramer said.

So far, the biggest clue linked to the killer is a car.

Authorities are looking for a “boxy,” two-door, late-model car that a neighbor spotted outside Clements’ home around the time of the shooting, Kramer said.

The witness said the car was running with no one in it Tuesday night. There are no street lights in the area.

Minutes later, the car was gone.

The car may be a dark-colored Lincoln or a Cadillac. A witness reported seeing a light green glow coming from the dashboard. The car was last seen Tuesday night traveling west on Higby Road before turning south onto Jackson Creek Parkway. Anyone who may have seen a car matching this description is asked to call authorities at 719-390-5555.

Investigators also want to speak with a woman seen speed-walking near Clements’ home not long before the shooting. The woman was wearing light pants, a dark windbreaker and possibly a hat. The woman is sought because she may have seen the suspect, Kramer said.

When asked whether Clements had received death threats, Alison Morgan, DOC assistant director of finance and administration, declined to comment other than to say, “Corrections is inherently a dangerous business.”

Morgan also wouldn’t say whether DOC provided Clements with personal security, including surveillance at his home and staff security outside his office.

She said all of Colorado’s prisons have been placed in modified lock-down as a result of the slaying. Inmate educational and work programming has been canceled temporarily for security reasons, she said. Visitation is curtailed until further notice.

Capt. Jeff Goodwin, spokesman for the Colorado Bureau of Investigation, said patrol officers increased staffing significantly Wednesday at the state Capitol, the governor’s mansion and the governor’s security detail.

“We have a responsibility to protect the governor and his family,” Goodwin said. “Other people at the Capitol benefit from that increased security, as well.”

The added security will continue for some time.

Sgt. Joe Roybal, spokesman for the El Paso County Sheriff’s Department, said investigators are following numerous leads, but so far none has led to a specific suspect.

“If we feel we’re close to identifying a suspect, we don’t publicize that because we don’t want to scare a suspect off,” Roybal said.

Clements’ death occurred a week after he denied a request by a Saudi national, Homaidan al-Turki, to serve out the remainder of a Colorado prison sentence in Saudi Arabia. He cited al-Turki’s refusal to undergo sex-offender treatment in his denial, The Associated Press reported.

Al-Turki, a well-known member of Denver’s Muslim community, was convicted in state court in 2006 of unlawful sexual contact by use of force, theft and extortion and sentenced to 28 years to life in prison. Prosecutors said al-Turki kept a housekeeper a virtual slave for four years in his home and sexually assaulted her. A judge reduced the sentence to eight years to life. Al-Turki insisted the case was politically motivated.

Al-Turki’s conviction angered Saudi officials and prompted the U.S. State Department to send Colorado Attorney General John Suthers to Saudi Arabia to meet with King Abdullah, Crown Prince Sultan and al-Turki’s family.

Dave Joly, Denver spokesman for the FBI, said agents are looking at all angles. He did not say if federal agents joined the investigation as a result of the al-Turki case.

“Nothing is off the table,” Joly said in an e-mail. “If a lead comes up in another state or out of the area, the FBI is here to assist in any way we can.”

Mike Knight, chief investigator for the Arapahoe County District Attorney’s office, said the prosecutors who worked on the al-Turki case and other high-profile investigations are taking increased security measures as a result of the slaying.

Knight would not specify what those measures are, but he said they were initiated by the DA’s office and not on advice of law enforcement.

“Out of an abundance of caution for the attorneys who worked on those cases, we wanted to make sure that they take precautions,” Knight said.

Roybal declined to say whether investigators are looking at the al-Turki connection.

Clements’ home, like others in the Bent Tree Subdivision, is nestled in woods, well off Colonial Park Drive.

Several neighbors told The Post they knew Clements lived in the subdivision, but they didn’t know the couple well. They said they didn’t see or hear anything unusual Tuesday night.

Hickenlooper appointed Clements in January 2011. He came to Colorado from Missouri. In Colorado he supervised a staff of 6,022 employees at 20 public prisons. There were 20,379 Colorado inmates as of the end of 2012.

Tony Carochi, appointed Wednesday as DOC interim executive director, wrote to all corrections employees.

“Even as the hours have passed since we first learned about the death of Mr. Clements, the shock and grief still feels unreal,” Carochi wrote.

“Obviously, the department is supporting (the investigation) any way we can,” Morgan said. “We won’t do anything to interfere and we will not speculate on any specific motive.”

Hickenlooper ordered all flags lowered to half-staff until the day after Clements’ funeral. In the afternoon, Hickenlooper met with DOC employees.

Kirk Mitchell: 303-954-1206, kmitchell@denverpost.com or twitter.com/kmitchelldp

Kieran Nicholson, Tom McGhee, Joey Bunch, Christopher Osher and Jeremy Meyer contributed to this report.