GRAND RAPIDS -- On many nights in the city's Northeast Side, a routine traffic stop provided inspiration for Grand Rapids Police Officer Joe Trigg to be a better cop and person.

Moments after Trigg would pull over a driver, fellow Officer Robert Kozminski would swing by to check on his friend, knowing that each encounter could turn dangerous.

"He would show up as my backup, just to be there for me," Trigg said Tuesday, two days after Kozminski was slain after responding to a domestic dispute. "I molded and modeled myself after him. He was a great guy, a caring guy, a great teammate."

For most of Trigg's six-year career, he and "Koz" were partners, sharing life stories, a passion for sports and, at times, talks of how an officer can lose his life in a moment.

Trigg took Saturday night off to attend a West Michigan Whitecaps game, taking him away from the last shift Kozminski, 29, would work. Jeffrey VanVels, 45, allegedly shot the patrolman early Sunday as he went to secure the rear of VanVels' house. At the time, police were trying to diffuse a situation in which the suspect reportedly had threatened his family.

"It shook my world," Trigg said of word that his friend was killed in the line of duty. "On any day, anything can happen ... He didn't waver in the way he did his job."

Trigg has run "what-if" scenarios in his head a million times -- what if he had been working, what if he had arrived at the suspect's house that night in place of his friend.

Each time he settles with the knowledge that nothing in his power could have prevented Kozminski's death. His friend would have taken the call at the VanVels' residence with the same vigor and conviction to help as he always displayed.

"I know there's nothing I could have done, but it doesn't stop the thoughts," he said, struggling with his emotions. "Any officer that would have went to that side of the house, it would have been the same outcome."

It was Kozminski's consistency that impressed Trigg when the two met early in each of their careers. Kozminski was working the center city and Trigg the Northeast Side. They'd often overlap on calls, eventually taking dinner breaks and finding common ground.

Kozminski soon bid to be moved to Trigg's patrol area. He found Kozminski an eager officer, taking calls so others could have a break. Kozminski was businesslike, but interacted easily with others, treating both victims and suspects fairly.

"He took his job seriously and did the best he could," Trigg said. "He did not take this job for granted."