She was a disciplined, fearless young woman of great promise, a Wesleyan University junior with a passion for women’s health issues. He was apparently disturbed, a man with shaky relationships and a malevolence toward Jews, threatening them and others on the campus in Middletown, Conn., in a journal he kept.

The lives of Johanna Justin-Jinich, 21, and Stephen P. Morgan, 29, had intersected briefly  and ominously  two years ago, when both attended a summer course at New York University. He called repeatedly and sent 38 harassing e-mail messages. The university and the police were notified, but he had left town and she declined to press charges.

There was no way to foresee the sudden, nightmarish sequel. Mr. Morgan walked into a campus bookstore about 1 p.m. Wednesday, then toward the Red and Black Cafe, where Ms. Justin-Jinich worked. He was a bearded, menacing figure on the overhead surveillance camera, a dark gun in his right hand swinging at his side, and something else hidden behind him in his left hand.

It was a long-stranded wig and he put it on, the baldish man undergoing a bizarre transformation as he confronted her, raised the gun and opened fire, a point-blank, seven-shot execution, officials said. Ms. Justin-Jinich fell, mortally wounded. The assailant  who the authorities said turned himself in to the police just before 9:15 p.m. Thursday  retreated the way he came in, dropping his wig, long-sleeved shirt and Czech-made CZ-USA 9-millimeter semiautomatic pistol.