He Knows You're Alone (1980)

A reluctant bride-to-be is stalked by a serial killer who only kills brides and the people around them. While her friends get whacked one by one, a hard-boiled renegade cop whose bride was killed years ago tries to hunt him down before it's too late for this bride. Meanwhile, she must figure out if it's all in her imagination or not--aided by her ex-boyfriend.