Police in North Carolina delayed for more than an hour after a chilling emergency call that captured a gunshot before sending officers to the home where a real estate developer killed his family and then himself.

Fayetteville Police spokeswoman Theresa Chance says the 74-minute delay before officers were sent to the home where William Maxwell shot and killed his wife and their two children on Monday is part of an internal investigation.

Police say Maxwell shot and killed his wife, Kathryn, and their two teenage children, Connor and Cameron, before killing himself.

Hours before the killings, friends and family gathered at the home to tell William Maxwell how much they worried about his recent demeanor that seemed far from his normal, upbeat self.