"Something fishy went down there," Johnson told the newspaper without providing any details. "I don't think it happened the way they're saying it happened. Somebody did something to him."
Police in Arapahoe County, Colo., have said McKinley, who was who was found dead Monday, died of a self-inflicted gunshot wound, adding that he had been depressed after having season-ending knee surgery last month.
That McKinley would even consider taking his life surprised the mother of his infant son, Keon.
Shayla Lites said she spoke with McKinley last week because their son was going to visit his father in Denver.
She knew McKinley was bothered that a second knee operation would keep him from playing for the Broncos this season. "But it's not anything he hadn't felt and overcome before," Lites told The Associated Press by telephone Thursday.
McKinley visited South Carolina two weeks ago, bringing Keon with him to South Carolina's 17-6 victory over Georgia on Sept. 11. McKinley was the Gamecocks' all-time leader in receptions (207).
Lites believed having Keon in Denver with him would take McKinley's mind off the injury. "Kenny always enjoyed being with Keon," Lites said.
Johnson said he can't believe McKinley would commit such an act with his son so close by him.
"He lived for his son," Johnson said.
Lites, 25, is a South Carolina graduate and currently is studying pharmacy at the Medical University of South Carolina in Charleston. She said she hasn't spoken with Colorado authorities about McKinley's death.
"I just hope they finish the investigation soon," Lites said. "They owe it to Kenny and to Keon."
Lites said she was attracted to McKinley's personality, much like most of his coaches, teammates and fans were. Keon has a similar smile and attitude, his mother said.
Keon doesn't understand the tragedy unfolding around him, Lites said. She already has thought about what she might tell her son when he begins asking about his father.
"I guess I'll try and talk about Kenny's life and not the end," she said.
The Associated Press contributed to this report.