The CBS News reports led Nashville authorities to release more information about the case.
But Keteyian said on "The Early Show" Thursday many questions remain unanswered.
Never-before-seen cell phone records obtained exclusively by CBS News revealed McNair's girlfriend, 20-year-old Sahel "Jenni" Kazemi had a much deeper relationship than previously disclosed with the man Nashville police say sold her the 9 mm pistol used to kill McNair, 36, a married father of four who was almost a year-and-a-half into retirement when he was slain.
Records show Kazemi and Adrian Gilliam Jr., a 33-year-old convicted felon, exchanged a total of 203 phone calls and text messages in the three weeks leading up to the deaths.
Gilliam was "absolutely not just someone she met who just sold her a gun," private investigator and former detective Wayne Black observed to CBS News.
And, says Keteyian, the cell phone records show Gilliam was one of the last people to speak with Kazemi alive, in a three-minute call he made on July 4, at 12:02 a.m.
In August, Keteyian I visited Gilliam at a Tennessee detention center. Cameras weren't allowed inside.
Speaking for the first time to a reporter, Gilliam would only say he'd first met Kazemi "downtown." He wouldn't discuss the nature of their relationship, but vehemently denied they were romantically involved.
Hours after Keteyian's first report Monday highlighted mistakes and inconsistencies in their investigation, Nashville police released a 14-page case summary, including information on 50 text messages between McNair and Kazemi in the hours before their deaths.
In one text, Kazemi asks McNair if he loves her. His response: "I love you, Baby."
Later that morning, Kazemi says, "Baby, I might have a breakdown, I'm so stressed." He tells her, "Everything gonna be OK." She then asks him for $2,000.
Kazemi's bank records, obtained exclusively by CBS News, show $2,000 was transferred into her account that same day -- July 3 -- leaving a balance of more than $2,500 -- and, says Keteyian, undermining a major police theory that money problems Kazemi was having somehow triggered the murder-suicide.
Kazemi's sister, Azadeh Kazemi, remarked to CBS News that she doesn't think "$2,000 is enough for someone to go that mad."
The police summary also reveals McNair may have been involved with a 25-year-old woman -- Leah Ignagni -- at the same time he was dating Kazemi.
Family and friends say Kazemi suspected McNair was cheating on her as far back as April -- and took it in stride.