HOLLADAY — Several unanswered questions remain after the fatal shooting that left one police officer dead and another injured Sunday. Chief among them: Why did 31-year-old Cory Lee Henderson turn his gun on police?

"Right now, I think it's trying to get answers, which everyone deserves," Unified Police Lt. Lex Bell said. "We need to know some things. I know (Doug Barney's) family wants to know why — why would this guy shoot and kill one of the most wonderful men you’d ever meet."

Barney, 44, a Unified police officer, was shot and killed in the deadly shootout Sunday. Henderson was also shot and killed.

Bell said police hoped to get answers from an unidentified woman who was with Henderson at the scene of a car crash earlier in the day.

The woman was found, interviewed and released Monday, according to Salt Lake police. Police said the woman was not booked into jail and that the investigation is ongoing.

Sunday's deadly encounter appears to have started shortly before 10 a.m. when a black BMW allegedly ran a red light and crashed into a white sedan near 2160 E. 4500 South.

Witnesses described seeing Henderson and a white woman with blonde hair get out of the BMW and leave the scene.

Barney, who responded to the car crash, spotted Henderson a few blocks away near 4200 S. Lynne Lane (2050 East), a quiet residential neighborhood.

The bloody shootout that followed unfolded in mere minutes, according to Salt Lake City Police Sgt. Robin Heiden.

Seven minutes after the call about the car crash, an officer radioed that shots had been fired and that an officer was down, Heiden said.

Three minutes after that, at 10:01 a.m., there was another call: Shots fired, suspect down, according to Heiden.

Police said Barney was shot once in the head. He was later pronounced dead at the hospital.

According to Bell, the 18-year law enforcement veteran's gun was still in its holster.

"There was no shootout there," Bell said. "He was just flat out murdered."

Henderson, the gunman, was shot multiple times and killed, according to authorities.

Unified police officer Jon Richey, 51, was also shot and wounded.

On Sunday, Gov. Gary Herbert ordered the U.S. and Utah flags to be lowered on the day of Barney's funeral.

Barney is the first U.S. police officer to be killed in the line of duty this year, according to the Officer Down Memorial Page, a nonprofit that tracks law enforcement officer deaths.

Last year, 129 law enforcement officers died in the line of duty, 39 of them due to nonaccidental gunfire, according to the organization.

Support for the fallen officer flowed in from around the country Monday. On Twitter, New York City Police Commissioner William Bratton posted a photo of Barney on Twitter and wrote, "Our prayers are with the family & colleagues of @UPDSL Officer Doug Barney."

Airline company JetBlue is also offering free flights to law enforcement agencies sending representatives to memorial services for Barney.

The Unified Police Department will hold a candlelight vigil for Barney and Richey from 6-10 p.m. Wednesday at Holladay City Hall, 4580 S. 2300 East.

Email: dchen@deseretnews.com

Twitter: DaphneChen_