(CNN) — A former Colorado inmate who was a white supremacist gang member is now the focus of the investigation into who killed the state's prison chief.
Tom Clements was gunned down Tuesday night when he answered the door at his home in Monument. Witnesses reported seeing a black, boxy vehicle near the house at the time.
The case took a dramatic turn Thursday when authorities in northern Texas tried to pull over a man driving a black Cadillac, triggering a shootout and a car crash that left the driver dead and a sheriff's deputy seriously wounded.
The driver was identified as 28-year-old Evan Ebel, a former gang member who was out on parole, according to El Paso County, Colorado, Undersheriff Paula Presley. He was released from prison in early February, according to a source close to Ebel's family.
Authorities say the car he was driving is the key link between Ebel and Clements' killing. It had two different Colorado license plates, authorities said, one in the front, and one in the back.
"There is evidence in that vehicle that will be of interest of us," Presley said.
The question is: What is inside the car?
A law enforcement official tells CNN that a uniform jacket for a pizza restaurant was found in the vehicle.
That seems key to why Denver authorities are also in Texas to examine the Cadillac. They are investigating the killing of a pizza delivery worker. On Sunday, Nathan Collin Leon, 27, disappeared from work in Denver and was found dead in nearby Golden. Leon's family said he delivered pizzas as a way to earn extra money for his wife and his three girls.
Denver investigators tell CNN there is a "strong connection" between the killings of Leon and Clements.
High-speed chase in Texas
On Thursday, Ebel sped through Montague County, Texas, near the Oklahoma state line, about 700 miles from Monument.
Deputy James Boyd tried to pull the car over, but it's unclear exactly why, other than it would have a been a routine part of Boyd's job.
Boyd did not know about the Clements case, authorities said.
Ebel shot the deputy twice in the chest, with another bullet grazing the deputy's head. Wearing a bulletproof vest, the deputy managed to call for help and to tell law enforcement which way Ebel was driving. Authorities say they have looked at the dashcam video of the shooting.
Boyd remains in serious condition at a Dallas-Fort Worth hospital.
The information the deputy gave allowed law enforcement to catch up with Ebel. A high-speed chase between them ensued, ending about 30 miles away in Decatur, Texas, with Ebel firing out of his window at police, law enforcement said.
"I would say he was running about 100 mph, and he had his left arm out the window and he was just shooting," said Decatur Police Chief Rex Hoskins, whose patrol car was parked in the median as the Cadillac raced past.
The chase ended when the Cadillac screeched onto another road and slammed into an 18-wheel truck, authorities said. With the front of his car crushed, the driver got out and started shooting again.
Ebel didn't hit any officers this time, they said. But they shot him.
He was taken to a hospital and kept alive on machines, but he died Thursday night, authorities said.
A prison conspiracy?
Since Tuesday, investigators looking into Clements' killing have told reporters they are considering numerous angles.
One is that Ebel, a former member of the 211s -- a white supremacist group -- might have conspired with other inmates to kill Clements, Presley said.
The Department of Corrections told investigators that Ebel was a prison gang member, she said on CNN on Friday.
Ebel has a lengthy criminal history, according Sheriff David Walker of Wise County, where Decatur is located. Records show that in 2005 Abel was convicted of felony menacing, assault and robbery. In 2006, Abel pleaded guilty to assaulting a detention officer, records show.
On Thursday, Presley said that investigators were considering the possible involvement of a Saudi national named Homaidan al-Turki.
Al-Turki's name was initially reported as possibly linked to Clements' death after a local news outlet cited an anonymous source saying that investigators were discussing al-Turki.
Al-Turki was convicted of sexually assaulting his housemaid at his Aurora, Colorado, home seven years ago.
This month, Clements denied al-Turki's request to serve the remainder of his Colorado prison sentence in Saudi Arabia, records show.
Presley said Thursday that investigators were trying to determine whether "there may have been some motivation or legitimate threat" related to al-Turki's case, adding that "we have not identified that specifically as a threat."
Al-Turki is now at the Limon Correctional Facility. CNN has not received a response to its requests for comment from his lawyers.
Late prisons chief described as 'amazing man'
Clements had been chief of Colorado's prison system for a little over two years. He took the job in January 2011 after working for 31 years as part of Missouri's Department of Corrections.
In his time in Colorado, he made a big impression.
"He was an amazing man, an amazing man," Alison Morgan, a spokeswoman for Colorado's Department of Corrections, said Thursday. "An inspirational leader."
Some witnesses said they saw a man driving a vehicle -- possibly a Lincoln Continental or a two-door Cadillac -- away from Clements' neighborhood a short time after the shooting. Others reported seeing a black, boxy vehicle with its engine running but no one inside on Clements' street.
Asked Thursday whether the prison chief's killing may have been a professional hit, Presley of the El Paso County Sheriff's Office said, "We don't have any specific information that would lead us to that."
The central Colorado county sheriff's major crimes unit said it has received more than 100 solid tips about the incident, including a growing number of witnesses describing a black car then in the area.
Meanwhile, mourning continues.
His funeral will be Sunday, Gov. John Hickenlooper's office said, and he'll be remembered at a public memorial service in Colorado Springs the next day.