One other victim remains hospitalized in unknown condition, Plano police told the local ABC affiliate.
Mr. Hight said that he and Spencer communicated mostly through texting and online messaging, and that Spencer had told him about the breakdown of his marriage in vague terms.
"After two years of trying to get him in treatment, trying to get him to stop, trying to help him... she said, enough is enough. I don't. I think 'why do people have to do this, ' you know?"
WFAA-TV reports that several of the people at the party had been mutual friends of Spencer and Meredith, including Dunlop, who was the best man at their wedding in 2012, and Morgan, who was a groomsman.
One of the victims, Meredith Hight, 27, was the estranged wife of the gunman, officials said Tuesday.
The grieving father told the newspaper he last saw Spencer and Meredith last Thanksgiving, before they separated, when he drove to Plano to visit them and see the house they had purchased the year before.
Monday afternoon Plano PD Chief Gregory Rushin held a press conference to notify media that an eighth victim had died at the hospital. Debbie Lane said Spencer lived in an apartment downstairs from Meredith. The two married in September 2011.
3 dead from apparent carbon monoxide poisoning in Florida
They told investigators that they had a running generator in their garage with the doors closed and fell asleep. A friend of the victims found a generator inside the house with the door slightly open, fire officials said.
Chester said he was also grieving for the other victims, and that some were his son's longtime friends. "What their families are going through right now is pure hell".
A passionate cook and hostess, Meredith Hight's football watching party on Sunday was to be the first gathering of friends she hosted on her own. It was the happiest she'd been in years.
"We said 'alright we're behind you 100 percent, '" Gene said. She had filed for divorce from her husband, Spencer Hight, in July, and the cookout would bring new memories into the Plano, Texas, house the couple once bought together but shared no more.
They both thought after the divorce perhaps Hight would be able to carry on independent of their daughter. "It's just a bad event", Rushin said.
"I don't think he was insane, I think we make choices consciously", Debbie Lane said. "I think he chose evil". His or her condition is now unknown.
Rushin noted that police are conducting a thorough investigation and will be interviewing as many people as possible, saying that a mass shooting like this isn't something law enforcement in Plano is used to.