FOR more than 50 years, Carl Ericsson secretly nursed a grudge against Norm John­son for putting a jockstrap on his head while joking around in the locker room of their high school. In January, the 73-year-old retiree tracked Johnson down at his home – and shot him dead.

“It seems unbelievable that he could hold a grudge for so long, but obviously he did – and all over a silly schoolboy prank,” police chief Chuck Pulford of Madison, S.D., told The ENQUIRER.

The incident reportedly hap­pened in the late 1950s when Johnson was a popular track star at Madison High School and Ericsson was the student sports manager.

Johnson went on to play college football and earn bachelor’s and master’s degrees. He eventually re­turned to Madison High where he taught and coached for more than three decades. The 72-year-old with two daughters and four grandchil­dren also sang in his church choir and was an avid Green Bay Packers fan.

Meanwhile, Ericsson graduated from North Dakota State Univer­sity and moved to Wyoming. He returned to South Dakota and settled about an hour away from Madison. Married for 44 years, he recently retired from a 25-year ca­reer in insurance.

The incident over the jockstrap seemed long forgotten, but shortly before the murder, Ericsson flew into a rage when his brother men­tioned Johnson’s name.

Authorities don’t think the two men had been in contact before Ericsson went to Johnson’s home on Jan. 31 and knocked on the door at 7:30 p.m. He asked his old classmate his name twice before shooting him twice in the face with a .45-caliber pistol, killing him instantly.

Johnson’s wife of 53 years heard the shots and ran to the door, where she found her husband lying on the ground. In the darkness, she saw a man hurriedly walking away.

Everyone was stunned to learn Ericsson’s reason for murdering Johnson.

“It’s beyond senseless,” said Ken­neth Meyer, the state’s attorney for Lake County, S.D.

Johnson’s youngest daughter Beth Ribstein, 50, couldn’t under­stand how Ericsson could hold a grudge for so long. “It was just goofing off in a locker room,” she said. Beth believed Ericsson had been envious of her father’s success and popularity.

“He was just jealous of Dad his whole life,” she said at her father’s funeral, which was attended by 600 mourners.

Ericsson pleaded guilty but mentally ill to a charge of second-degree murder on June 15. He was sentenced to life in prison without parole.

Before he was led off to jail, white-haired Ericsson said in a frail voice: “I’d like to tell Mrs. Johnson how very sorry I am for what I did. I just wish I could turn the calendar back.”