When 23-year-old Kenny McKinley lay down on his bed, put a semi-automatic to his head and pulled the trigger, Brady Quinn blamed himself.

After all, Quinn, McKinley's Denver Broncos teammate, knew McKinley had debt, depression and a gambling addiction. They'd talked about it. Quinn was trying to help him. "He'd assured me everything was in order," Quinn says.

But in the summer of 2010, wide receiver McKinley was placed on injured reserve, and they didn't talk as much. Quinn was busy trying to win the starting quarterback job. Next thing he knew, it was Sept. 20, and Kenny's name was in 48-point font in the newspaper.

"I had a sense of guilt," says Quinn, now 28. "It was like, 'Where did I miss it? What did I not see? Was there a conversation where I wasn't as truthful as I could've been?' ... I vowed that I'd never let that happen to a teammate again."

But 26 months later, it did.

Kansas City Chiefs linebacker Jovan Belcher shot his girlfriend, Kasandra Perkins, several times, drove to the team's headquarters, ducked behind a car and put a bullet through his head. That was two weeks ago. It was the seventh suicide of a current or former NFL player in the past two years.

Quinn was wracked again.

"We'd just been together," says Quinn, now a Chiefs quarterback. "I'd just seen him and his girlfriend and his little girl, Zoey, at the stadium. We were talking about how she was doing, how cute she was. And now ... "

And now he had to go out and try to win a football game. Somehow, he led the Chiefs to an astonishing win over the Carolina Panthers. But when he made it to the podium afterward, he looked like he'd lost everything.

"When it happened, I was ... thinking, 'What could I have done different?' " he glumly told a room full of reporters. "We live in a society of social networks, Twitter pages and Facebook and that's fine. But it seems like half the time we're more preoccupied with our phones instead of the actual relationships in front of us. When you ask someone how they're doing, do you really mean it? When you answer someone back how you are doing, are you telling the truth?"

That hit me like a two by four across the forehead.

A sportswriter friend of mine, Mike Penner, was having troubles. But he stopped returning my emails and texts, so I figured he wanted to work on his problems on his own. Then, the day after Thanksgiving in 2009, they found him in his car with a hose going from the exhaust pipe to the window.

Are we our brother's keeper? Our teammate's? Our colleague's? Do we have a duty to help people even if they're not asking?

Just before the Super Bowl nearly four years ago, former All-Pro Denver Bronco Karl Mecklenburg was shocked to hear that former teammate and hunting buddy Shane Dronett had shot himself. He'd never told Mecklenburg he was hurting.

Karl Mecklenburg says that despite the bonds teammates develop, there are still too many things they just don't discuss. US Presswire

"You think you have this bond as a teammate," Mecklenburg says. "You go through all this stuff together, you get through injuries, you get through losses, you feel like you can say or do anything with that person, but it's not the case."

These are pro football players, hard men who won't even tell a coach their knee is killing them, much less their heart.

"We don't admit that kind of stuff," Mecklenburg admits. "If I was feeling sick before a game, I was going to play. It's my coach's job to find out and replace me. Sometimes, I'd be out there and knocked so dingy I couldn't even see the sideline, but I wouldn't come out. I'd have to ask the guy next to me what the call was. So nobody's going to tell his teammate, 'Hey, my wife's cheating on me. My daughter's having problems.' Not going to happen."

What did happen was that 39 months after Dronett, Mecklenburg's good friend San Diego Chargers linebacker Junior Seau committed suicide by shooting himself in the chest.

"You keep asking yourself, 'Why didn't I call him? Why didn't he call me?' " Mecklenburg says. "If he'd have called me and asked for help, I'd have been on the first plane out. Me and a hundred other guys. But he didn't."

So if Jovan Belcher was having problems with his girlfriend; if O.J. Murdock of the Tennessee Titans (suicide: July 30, 2012) was depressed because of his injuries; if former Chicago Bear Dave Duerson (suicide: Feb. 17, 2011) was having headaches, they weren't going to tell somebody on the team. They were going to stay bulletproof. They'd outrun every problem before, why stop now? And then it stopped them.

It leaves NFL players wondering who's going to turn up in the morgue next.

"It makes you feel like there's a time bomb inside of you," says Mecklenburg, 52. "It's like Russian roulette. As it is, I park in the same spot in the airport every time, so I don't forget. I take a cellphone picture of my hotel room number so I don't forget. I don't know what kind of damage has been done. You worry about what friend it's going to be in the newspaper next. Or if it's going to be you."

I still regret not trying harder to find my friend Mike, to go to his place, to break through, to keep him from taking that last, grisly step. Quinn feels that sorrow, too, but it's only made him redouble his vow.

"You can't feel guilty about things you can't control," he's decided. "The only thing you can do is make the contact you have with people as meaningful as you can. Maybe the way you treat somebody with respect makes him feel better that day; maybe it keeps him from doing something to himself. You never know."