The first reports Sunday night were brief and vague — a “homicide investigation” was underway at a house on Spring Creek Parkway, between a middle school and a retirement home.

Roads were closed, police said, so expect traffic delays in the morning.

But even those scant details were enough to alarm the residents of Plano, Tex., a sprawling suburb of quiet homes and big parks many miles north of Dallas.

And alarm turned to horror as details filtered out Monday. In the afternoon, the chief of the Plano Police Department, Gregory Rushin, announced that there was not just one dead from that house — but nine, including a gunman who brought “mass murder” to an NFL watch party.

“They were having a cookout. They were getting prepared to watch the Cowboys football game,” Rushin told reporters. “We’ve never seen anything like this in our city before.”

The host of the party was Meredith Lane, 27: the only victim named, and then only by her family.

“She was our only child,” Gene Lane told The Washington Post, as he traveled with his wife to Plano on Monday. “All we know is she is gone.”

Lane bought the house two years ago with her then-husband, whom she filed to divorce in July. On her Facebook page, she had advertised for a roommate.

“She was a cook, and a quite fine one, and she loved hosting friends and families,” Lane’s mother, Debbie, told ABC affiliate WFAA. “This was her first opportunity to do it after the divorce.”

Police have not released any details about the dead suspect, except to say that he “had ties to that residence.”

Laughter and the smell of a grill filled the street as the party kicked off in the afternoon, neighbors told reporters. People in Cowboys jerseys were seen filtering in and out of the house.

Even that was more ruckus than usual for Crystal Sugg, who works at an assisted-living center down the street. “There’s nothing that ever happens over here,” she told The Post. “It’s like they say, quiet as a mouse.”

But as the sun began to set, Sugg stepped outside for a cigarette and “heard a commotion.”

She walked up the street in the half-light, until she could make out the figures of a man and woman in front of the house, locked in an argument.

Sugg couldn’t really hear them.

“”They were having an altercation,” she said. “It was low at first, but started to get louder.”

Sugg smoked and watched for several minutes as the volume increased. Eventually, she said, the woman tried to break away from the man.

Then it all happened very fast.

“She was going into the house,” Sugg said. “He was coming right behind her.”

And then, from somewhere behind him, the man produced what looked to Sugg like a rifle. At the news conference later, the police chief said the shooter brought “multiple firearms of different types.”

Sugg started running when the gun came out and heard gunfire begin almost immediately.

“Thirty to 40 rounds, I heard,” she said.

And amid the shots, screams.

Sugg reached home and dialed 911. Several people did that evening, police said, and in about two minutes, the first of many officers pulled up to the house.

“The officer showed great bravery,” said Rushin, the police chief. He approached the house through the back yard, where he saw people lying wounded.

Inside the house: more gunfire, and the gunman.

A neighbor told the Dallas Morning News that she opened her door that night to the smell of gunpowder. She heard someone yell, “Hands up!” then a final volley of shots.

The officer killed the gunman immediately, Rushin said. Other men and women lay shot, all around the house.

Police and paramedics tried CPR on the wounded, but besides the gunman, seven would die in that house, and another on Monday at a hospital, where one more victim is still fighting to recover.

No names have been released by authorities. As of Monday afternoon, police said, some families had not yet been notified.

“We’re still shy of details,” Rushin told reporters. “I apologize for that. There’s so much to do when you have this many victims.”

But word of what had happened spread throughout the once-quiet suburb of Plano, and beyond, and horror followed the news.

“I’m friends with probably everyone that was in that house,” a man who approached a neighbor at the scene said in the wake of the carnage, according to the Morning News.

He was later spotted talking to an officer, the paper reported, “doubled over” in pain.

This story has been updated.

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