MONUMENT, Colo. (AP) — Colorado's top state prison official was shot and killed when he answered the front door of his house, setting off a hunt for the gunman and raising questions about whether the attack had anything to do with his position.

Authorities are also looking for a dark-colored "boxy" car seen near the house of Tom Clements, 58, when he was shot around 8:30 p.m. Tuesday in Monument, north of Colorado Springs. The vehicle's engine was running and a witness reported seeing one person driving away in the car.

Lt. Jeff Kramer of the El Paso County Sheriff's Office said investigators have not ruled anything out, but the shooting could have been related to Clements' job as executive director of the Colorado Department of Corrections.

"As the director of the Department of Corrections or any similar type position, it could in fact open someone up to be a target of a crime such as this. Although we remain sensitive to that, we also want to make sure that we remain open-minded to other possibilities as well," Kramer said.

The FBI and the Colorado Bureau of Investigation have joined the case, he said.

Colorado Gov. John Hickenlooper appointed Clements to the post in 2011 after he served for more than three decades in the Missouri Department of Corrections. He replaced Ari Zavaras, a former Denver police chief who led the department under two governors. The department operates 20 adult prisons and a juvenile detainment system.

Hickenlooper was red-eyed and somber and spoke haltingly Wednesday morning at a news conference in which he said he doesn't think the killing was part of any larger attack against his cabinet, members of which stood behind him, several of them crying. Others dabbed their eyes.

"Corrections is a very different job. You make difficult decisions every time that affect different people," Hickenlooper said, calling Clements dedicated, funny, caring and an expert on the latest and best methods in his field who chose the Colorado job over retirement.

"Tom Clements dedicated his life to being a public servant, to making our state a better place and he is going to be deeply, deeply missed."

Hickenlooper planned to go to Monument to meet with Clements' family after signing gun-control bills.

A family member called 911 to report the shooting. Search dogs were called in to comb through a wooded area around Clements' home, and authorities were going house to house trying to find out what neighbors heard and saw.

Clements lived in a wooded neighborhood of large, two-story houses on expansive 2-acre lots dotted with evergreen trees in an area known as the Black Forest. Long driveways connect the homes to narrow, winding roads that thread the hills. Clements' home was out of view, behind a barricade of crime-scene tape in the road.

It would have been simple to find where Clements lived. It took two clicks to get his correct street address through a publicly available internet locator service Wednesday morning. The listing also included his previous home address in Missouri.

After Clements was appointed, Hickenlooper praised Clements for his approach to incarceration, saying he relied on proven methods to improve prison safety inside and programs that have been shown to improve successful outcomes after offenders are released from prison.

While Clements generally kept a low profile, his killing comes 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.

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. He owned a company that some years ago sold CDs of sermons recorded by Anwar al-Awlaki, killed in a drone strike in Yemen in 2011.

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.

After Clements' shooting, someone with the State Department called the Colorado Corrections Department.

Prisons spokeswoman Alison Morgan said she had no details on the call other than to say it wasn't connected to the shooting investigation and may have been a simple courtesy.

"They called us because we have a cooperative international program with them," she said.

Hickenlooper ordered flags lowered to half-staff at public buildings until the day after Clements' funeral. Arrangements are pending.

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