What we know and don’t know about the incident.

Department of Public Safety Trooper Tyler Edenhofer was shot and killed Wednesday night during a fight along Interstate 10 west of Phoenix.

Several motorists had been trying to corral a man who was throwing rocks at passing cars. The altercation escalated as law enforcement officers arrived at about 10:30 p.m. Minutes passed. And then came a call on the radio to dispatchers.

“Shots fired, officer hit!”

“One DPS unit injured, unresponsive.”

By the time the scene was contained, Edenhofer, a trooper in his final days of training, was fatally wounded. Two other troopers were hurt and a department was left reeling.

The suspect has been identified as Isaac D. King, 20. Questions abound. But here’s what we know — and what we don’t — so far.

Why were police called to the area?

Department of Public Safety officials and radio communications say troopers were responding to reports of a “man in a white shirt” throwing rocks at cars traveling east on I-10 near Avondale Boulevard.

Initial 911 calls came in about 10:17 p.m. Passers-by stopped to try to calm the man and move him away from traffic, and DPS troopers arrived shortly thereafter, said Col. Frank Milstead, director of the Arizona Department of Public Safety.

Three state troopers

Trooper Dalin Dorris was the first to arrive at the scene and made contact with the man, officials said.

Troopers Sean Rodecap, along with Edenhofer, arrived about a minute later. Rodecap, who had been training Edenhofer, was in a T-shirt and jeans — in the final days of police training, instructors assume more of a bystander role and give more control to the trainee.

Edenhofer was hired in September after serving in the U.S. Navy, officials said. He graduated from the Adground vanced Trooper Academy on May 4.

Dorris and Rodecap joined the department in 2005 and 2008, respectively.

What exactly happened?

Details about the incident were released incrementally Thursday.

Milstead said Thursday afternoon that his troopers fought with King for eight minutes. During the scuffle, King was able to grab Rodecap’s duty weapon, which was in a leather, non-retention holster with a snap top fixed to his belt, Milstead said. He was not wearing a typical duty belt, which includes a stronger internal locking feature.

He fired the gun, striking Dorris in the shoulder, leaving a through-and-through wound, officials said.

Edenhofer was also shot in the shoulder, but the bullet “ricocheted” within his body, causing fatal wounds, Milstead said.

Rodecap was also hurt in the fight. According to DPS emergency communications, approximately six minutes passed between when a trooper reported “shots fired” and when someone said the subject was “in custody in the back of the patrol car.”

Two officers with the Goodyear Police Department arrived moments after the shots were fired and worked to help the on-scene troopers, said Lisa Berry, a department spokeswoman.

It’s not clear how King was able to wrangle Rodecap’s gun, Milstead said, citing the continuing investigation.

How hurt were the other troopers?

Dorris and Rodecap were treated and released from a hospital Thursday morning.

Who is the suspect?

Authorities say Isaac D. King was taken into custody after the incident and, as of Thursday afternoon, was being treated at a hospital for undisclosed injuries.

Milstead said King does not have a criminal backArizona but that he has experienced mental health issues.

“He has mental health history. He apparently was on medication for anxiety and depression,” Milstead said

King’s mother told investigators that she last saw him jumping on a trampoline in the backyard of their Avondale home at 9:30 p.m.

Department of Public Safety officials would not discuss the extent of his injuries.

How common are shootings like this?

Not very.

The shooting was the first time a DPS trooper was killed in the line of duty in five years, spokesman Raul Garcia confirmed. The last death happened on May 6, 2013, when Trooper Timothy Huffman, 47, was fatally struck by a tanker truck on Interstate 8 about 40 miles east of Yuma.

Edenhofer was also the second Arizona police officer to be slain on duty this year. Nogales Police Officer Jesus “Chuy” Cordova was fatally shot April 27 as he approached a robbery suspect in front of a border-town grocery store.

Edenhofer was the 88th law enforcement officer in the United States to die on duty this year, according to the Officer Down Memorial Page, a group that tracks police deaths. Thirty-six deaths this year were from gunfire.

Did law enforcement fire any shots?

Officials said troopers and other responding police officers did not fire any shots during the altercation.

What now?

DPS is leading the criminal investigation into the shooting and will eventually present the case to the Maricopa County Attorney’s Office.