RIDGEFIELD, Conn. — It is a sadly familiar story: A police call to an apparent disturbance; a sudden encounter between an officer and a suspect believed to be armed; a snap decision; pops of gunfire and the terrible aftermath of blood and regret.

But after officers were called to the Fairfield County home owned by John Valluzzo last week, it was as if the expected story line evoking Amadou Diallo or other police killings had been turned on its head. This time the person who was shot was a successful 75-year-old businessman and philanthropist, and the policeman a well-liked veteran who was a rare minority officer in a virtually all-white department. The setting was not a dark city street but a 9,000-square-foot estate in a green, historic Connecticut town whose residents have included Eugene O’Neill, Judy Collins and Henry Luce.

And if details of the shooting remain uncertain, the impact was devastating, especially for friends and relatives of Mr. Valluzzo, a hands-on dynamo who knew his way around a factory floor, tank engine, osso bucco recipe and museum-quality rare-book collection. He founded, nurtured and helped finance an improbably ambitious military museum in Danbury, and his death on the Friday before Memorial Day in its timing and its horror left friends gasping after answers.

“The story everyone has heard seems pretty odd and unfathomable,” said Samuel Johnson, executive director of the Military Museum of Southern New England, which became one of Mr. Valluzzo’s passions. “But if you knew John it’s 10 times more unfathomable. He was all about making everything better. He was a wonderful person. Never violent. To be honest, I can’t imagine what he’d be like violent. The whole thing makes no sense. All I can think is that it’s a terrible mistake.”