Moments after 54-year-old Sharon Gerot was fatally shot while riding on a lawn mower in her backyard in Riverside, her companion Thomas Lee Hansen is accused of telling a witness, “I shot ‘em.”

Thomas Hansen

Prosecutor Andrew Prosser told a 14-person jury about that admission during opening statements of Hansen’s first-degree murder trial on Tuesday.

Prosser said Hansen, who lived with Gerot, later was overhead saying that he “just couldn’t take it anymore.” Prosser said evidence will show what Hansen used to kill Gerot, where he was standing when he fired the fatal shot and how long Hansen had to meditate the killing.

But, defense attorney John Robertson, told jurors that not every killing is first-degree murder and that jurors should keep their minds open as they hear the evidence.

Hansen, 72, of Riverside, is accused of shooting Gerot with a semi-automatic handgun on May 1, 2011, according to a criminal complaint. Investigators said the pair had been living together for years and had been arguing earlier that day, according to court records.

The couple was planning to go work at Yellowstone National Park, investigators reported.

Hansen retired as Johnson County’s emergency management coordinator in 2007. He worked for the Iowa City Fire Department before that.