Despite having faced dangerous situations during his nearly 25 years as a sheriff's deputy, Sgt. Kenneth Gary Vann never needed his gun to defend himself.

Early Saturday, when he needed that weapon most, Vann didn't have the chance to ward off an unknown motorist who drove up beside his marked cruiser and fired repeatedly without warning, killing him.

Authorities said Vann, 48, was stopped at a red light on the East Side when someone ambushed him — an attack so sudden he was unable to reach for his weapon or call for help.

“He did not have a chance to do anything, hit the emergency button on his radio, or even to defend himself,” Bexar County Deputy Chief Dale Bennett said. “That car pulled up and started blasting, just like that. So where we are right now is that it looks like an ambush.”

Bennett described the murder weapon as “very probably high-caliber, and likely a semiautomatic.”

“None of us can see any reason behind this,” sheriff's Sgt. E.M. Conger said. “It has been hard on all of us. As for his friends and family, the biggest question we are all trying to figure out is why this happened to him.”

His wife, Yvonne, said she knows the risks that come with wearing a law-enforcement uniform, since she wears one herself. Still, she said she didn't see this tragedy coming.

She said that despite his long career, Vann never had used his weapon to defend himself, so she figured the worst news she might get was that he was injured in a crash.

“I never thought I'd get the call that he was dead,” she said, shaking her head in disbelief.

Vann was the first Bexar County deputy killed in the line of duty since 2003, and the 17th since 1840. Less than two weeks ago, Bexar County law officers gathered to honor the previous 16 killed on duty.

The last deputy to die on duty was Jesus Garza, 33, killed when he lost control of his patrol car near Calaveras Lake and slammed into a stand of trees on Dec. 26, 2003.

Late Saturday, authorities still were trying to piece together the events that led to Vann's fatal shooting near Rigsby Avenue and Loop 410.

A mobile command post — with members of the Sheriff's Office, the San Antonio Police Department, the U.S. Marshals Service, U.S. Immigration and Customs Enforcement, the Texas Department of Public Safety and the FBI — was set up in the parking lot of a nearby Walmart.

“This is where we are trying to put all the pieces of the puzzle together,” Bennett said as a new crop of officers prepared to gather evidence and interview witnesses.

Bennett said authorities were trying to find a small, white car seen in the area after the shooting, about 2:12 a.m. Investigators were securing surveillance camera images from two nearby convenience stores to see if the incident was captured.

Chief Deputy Sheriff Manuel Longoria said Vann was responding to a call for an accidental shooting in eastern Bexar County. He had stopped for a red light in the left westbound lane on Rigsby, just east of the Loop 410 overpass, “when someone rolls up on his right and just opens up, firing multiple shots.”

The bullets shattered the front and rear passenger windows. Authorities said they were not sure how many bullets were fired; Longoria said numerous spent cartridges were recovered around the shot-out cruiser.

He said Vann died before emergency responders could get him to a hospital.

“This is just a senseless thing,” Longoria said. “It really feels bad when one from your own agency is killed.”

At the scene, debris and shattered glass marked where the shooting started, Longoria said.

Once the shooting stopped, the sergeant's patrol car, still in gear, rolled into the intersection and came to rest against yellow crash barrels underneath the overpass' support pillars, Longoria said.

One person who was pulling into a nearby convenience store told investigators she heard two distinct, rapid bursts of gunfire.

Fellow deputies described Vann as well-liked and a hard worker.

They said he was a devout family man who was committed to his wife — also a sergeant with the Sheriff's Office — and his three children from a previous marriage: a 25-year-old daughter and two sons, ages 19 and 15. They said he enjoyed traveling and spending time with them.

“He worked nights, and on a Friday night during football seasons, it was understood he'd be coming in late because he was watching his boy play football,” said Sgt. Blake Johnson, who said Vann was a close friend he'd known at least 16 years. “His dedication to his family was very strong.”

The couple met in 1994, Yvonne was in training and Vann was a patrol officer. Yvonne thought he was handsome. She remembered chuckling when he tried kicking down a burglary suspect's reinforced door, to no avail.

Yvonne, the rookie, ended up going around the back, entering the residence through a sliding-glass door.

As everyone searched the premises, she noticed a bunch of wet clothes lying around. On a hunch, she opened the dryer — and found one of their burglary suspects. They called him the Maytag kid.

The couple didn't date for a long time — Kenneth was married, and even after his divorce, he and Yvonne still were just colleagues.

But a fellow deputy prodded them to give it a shot, and eventually they did.

They watched “The Bourne Identity” on their first date and shared their first kiss that night. They married June 14, 2008.

Vann owned land in Comal County and built a home where he and Yvonne forged a new life together.

They loved to travel and bought a motor home, which they drove all over the country. Kenneth drove at night, Yvonne drove during the day.

The veteran deputies liked anything having to do with Disney.

The last time they saw each other was Friday evening. Kenneth was getting ready to leave for work and noticed Yvonne had removed bulky bandages from a nose surgery.

“Oh, look, I get to kiss you today,” he said.

They kissed goodbye three times. Yvonne remembers each one. Then her husband walked out the door to go to work.

Staff Writer Jazmine Ulloa contributed to this report.