Months after being thrust into a national spotlight as the face of Howard County’s response to a murder-suicide at The Mall in Columbia, Police Chief William J. McMahon said Thursday that he will retire in June, after 28 years with the department.

McMahon, 51, who has served nearly eight years as chief, said he had picked the date four years ago, when he signed up for a deferred retirement payment program.

“The timing is just right,” McMahon said in a telephone interview. “I had some long-range plans that this would be the date. . . . I’m blessed. I still love what I’m doing, day after day.”

McMahon said Maj. Gary Gardner, a 30-year member of the department, has been named by Howard County Executive Ken Ulman to take command of the department of 649 full-time sworn and civilian employees with a budget of just under $100 million.

McMahon was acting chief when Ulman named him to the top job soon after he was elected in 2006.

“I think the world of him and the job he’s done,” Ulman said Thursday. He credited McMahon for innovations that helped to reduce crime and for his steady, calm leadership after the mall shooting on Jan. 25.

As one of the first ranking officers on the scene at the mall that Saturday, McMahon supervised scores of police officers from Howard and other jurisdictions, then delivered news updates before dozens of reporters, photographers and videographers on an event that attracted national coverage. Two people were killed that day, and the gunman fatally shot himself.

Last month, McMahon held a news briefing to review the evidence police had gathered. He described the gunman as a young man in declining mental health who was preoccupied with violence, particularly the Columbine High School mass shooting in Colorado in 1999.

The two killings and a suicide in one day in Columbia took place in an affluent suburban county of 300,000 people that ordinarily experiences four or five homicides a year.

McMahon, who joined the department as a patrol officer in 1986, is set to depart after years of falling crime in the county. He attributes that in part to efforts under his administration to crack down on repeat offenders and domestic violence.

“I’m very, very proud of what our crime numbers look like compared to what they looked like in 2006,” McMahon said. He said the number of overall crimes is down about 9 percent between 2006 and 2012 — auto theft down by half, robberies cut by a bit more than a third, burglaries down 10 percent.

The county had never seen a killing in the mall since it opened as a central shopping spot for the planned community of Columbia in 1971.

That changed when a 19-year-old man with a shotgun killed two people who worked in the Zumiez skate shop on the upper level, wounded another person, then shot and killed himself. No connection was found between the gunman, Darion Marcus Aguilar, of College Park, and the two people he killed, Brianna Benlolo, 21, and Tyler Johnson, 25.

County Council member Mary Kay Sigaty said the calm presence of McMahon that national TV audiences saw that Saturday was no act.

“That is who he was in the midst of that,” Sigaty said.

— Baltimore Sun