Denver Broncos wide receiver Kenny McKinley had a gambling problem and was deep in debt when he committed suicide on Sept. 21, friends and family told authorities during a probe into his death.

McKinley committed suicide with a gun he had purchased months before from teammate Jabar Gaffney, who told investigators McKinley wanted the weapon for his own protection, according to an investigative report by the Arapahoe County Sheriff’s Department that was obtained by The Associated Press. Arapahoe County Sheriff Grayson Robinson said there was nothing inappropriate about the sale of the gun.

Detectives also determined that McKinley had spoken about suicide with at least three of his friends, including former Broncos backup quarterback Tom Brandstater. Brandstater told investigators he had lent McKinley $65,000 and that McKinley owed $40,000 in casino markers in Las Vegas.

McKinley, 23, suffered a season-ending left knee injury during the first week of Broncos training camp. He underwent an operation several weeks before he shot himself in the left temple at his rental home near the Broncos’ practice facility. McKinley had injured the same knee in the Broncos’ next-to-last game in 2009.

The 131-page report, which states the investigation has closed, quoted witnesses as saying McKinley was depressed over his second knee surgery in eight months and was worried about how he would care for his toddler son when his football career was over.

Days before his death, McKinley had been ordered to pay $3,000 a month in child support by a South Carolina court. He had told friends he was being threatened with a paternity suit by another woman who said she was pregnant with his baby, according to the sheriff’s report.

McKinley had missed a South Carolina court hearing in the child support case on Sept. 14.

The Broncos declined to comment on the sheriff’s report out of respect for McKinley’s family.

McKinley’s parents and Brandstater told investigators they had been trying to help him fix his financial problems.

According to investigators, the Broncos were apparently aware of McKinley’s financial troubles.

The team’s player development director, Harold Chatman, had been asked by Brandstater’s representative to hold onto a copy of a contract Brandstater had with McKinley, stating McKinley would repay the $65,000 loan.

The Broncos called it an internal matter. A message was left by the AP on Wednesday with Brandstater, who is now on the Miami Dolphins’ practice squad.

The knee injury was costly financially for McKinley, who signed a four-year, $1.95 million contract with the Broncos in 2009 after they drafted him in the fifth round out of South Carolina.

The deal included a $200,200 signing bonus, and he made the rookie minimum salary of $310,000 last year. However, he had a split contract, meaning that because he was to spend all of 2010 on injured reserve, he would receive $240,000, instead of $395,000.

There were no guarantees that he’d recover from his second knee operation to earn the $480,000 due him in 2011 or $565,000 in 2012.

McKinley’s agent, Andrew Bondarowicz, told the AP that under NFL players’ association rules he couldn’t get involved with McKinley’s finances and thus could not discuss them.

Bondarowicz did say that McKinley had taken out a $50,000 loan from another, unidentified party, something that a former Broncos teammate, Everette Pedescleaux, had mentioned to investigators.

The sheriff’s report quotes McKinley’s father, Kenneth McKinley, as saying that he and his wife were getting many letters for their son at their home in Mableton, Ga., from casinos in Las Vegas. He said bill collectors also were calling his house asking for his son and that he had spoken with his son about managing his money better.

The elder McKinley said he also suspected his son was having financial problems because he had only recently begun using a credit card that he’d given him in college.

Kenneth McKinley did not return a message left Wednesday by the AP.

Brandstater told investigators that McKinley had a “major gambling problem” and that he told him that he owed $40,000 in Las Vegas. He said the two of them had dinner for 10 straight nights in May trying to “hash out ways to fix it.” Brandstater told investigators he eventually lent McKinley $65,000 and that he nearly emptied his bank accounts to help out his friend. McKinley was supposed to send Brandstater $7,500 from each paycheck but hadn’t paid back any of the money, Brandstater said.

Brandstater said he trusted McKinley to repay him but that his financial adviser insisted that a contract be drawn up and that a copy be given to the Broncos. Part of the pact included McKinley providing the title to his two vehicles as collateral.

He said McKinley also gave him two watches, a Breitling and a Gucci valued together at $30,000, as well as a gold necklace to hold as collateral.

Brandstater said he returned the necklace to McKinley, who sold it for $6,000. Brandstater told investigators he told McKinley to keep that money because he was in such dire financial straits.

Brandstater told investigators that about a week before he lent him the money, McKinley said “that he could save everyone the burden and just kill himself.”

Brandstater said it was awkward and they laughed it off.

Two women who were baby-sitting McKinley’s toddler son when they discovered he had killed himself each told investigators that McKinley had talked about suicide.

The mother of McKinley’s child, Shayla Lites, told investigators that a family court in South Carolina had ordered McKinley to pay $3,000 a month in child support, a figure that was based on his 2009 earnings. She said he was supposed to provide documents to the court showing his current salary. She said McKinley had been paying her $1,500 a month — and that she planned to return anything over that amount to him because she knew he had financial problems.

Gaffney, a Broncos receiver, told investigators he sold McKinley a gun in April. Gaffney had bought the gun in 2004 in Houston.

“Kenny told me he wanted a gun for his personal protection and being that I have a couple of legally owned firearms, I sold him one of mine that I didn’t want anymore,” Gaffney said in a statement to deputies.

Gaffney wasn’t in the Broncos locker room during the 45-minute media access Wednesday.

— AP Sports Writer Pat Graham contributed to this report.