OVERLAND PARK, Kan. — After the Sunday afternoon mayhem, the handcuffed suspect was led to a gun-gray police car, his beard salt and pepper, his T-shirt a striking white. He looked like who he was, in part: a retiree who was said to have just spent part of his weekend at a casino. Then, from the back seat, he shouted a hoary phrase tinged with a Southern inflection:

“Heil Hitler!”

Once again, Frazier Glenn Miller, 73, for decades one of the country’s more prominent white supremacists, known for his particular antipathy toward Jews, had announced himself. This time, though, he had been arrested here on suspicion of shooting and killing three people outside two Jewish community facilities, on the day before Passover.

The victims were William Corporon, 69, a physician; his 14-year-old grandson, Reat Underwood; and Terri LaManno, 53. None of them were Jewish.

The news of Mr. Miller’s arrest almost, but not quite, surprised Heidi Beirich, the director of the Intelligence Project at the Southern Poverty Law Center, which monitors hate groups. Ms. Beirich has had several telephone conversations with Mr. Miller, whom she described as both congenial and so virulent in his anti-Semitism that his hatred took her aback.

“On the one hand, I’m a little surprised,” Ms. Beirich said. “He has emphysema, spent most of his time posting nasty things on a website and hadn’t done anything in years. On the other hand, how can you be surprised when a guy who’s spent his life saying the Jews should be killed decides to go kill Jews?”