KANSAS CITY, Mo. (AP) - Jovan Belcher walked off the field after his final practice, laughing and joking with Chiefs defensive tackle Shaun Smith about who would get into the game the most on Sunday afternoon.

The two walked down the half-dozen steps and into the training complex, past the inspirational signs that coach Romeo Crennel regularly posts on the wall, and through locker-room doors.

Never could anybody imagine it would be Belcher's last time.

``We was joking, having fun,'' Smith recalled quietly. ``I'm going to miss him.''

Friends and family of Belcher and his slain girlfriend, Kasandra Perkins, tried to come to grips Monday with the horrible events of the weekend. As they did, a portrait of the 25-year-old player began to emerge, that of a man devoted to his family, who cherished his daughter and loved football after making it to the NFL against long odds. Still, the question remained: What would drive him to gun down the mother of his baby girl and then take his own life?

``I didn't see anything at all,'' said his close friend and fellow Chiefs linebacker Derrick Johnson, who couldn't bring himself to refer to Belcher in the past tense.

``Jovan is the definition of a teammate. He's going to give 100 percent every time,'' Johnson said. ``He and I have grown really close since he's been on the team, and this is devastating.''

Investigators were still searching for a motive behind Saturday's shootings.

Belcher shot the 22-year-old Perkins multiple times in a home not far from where he played, and then drove to Arrowhead Stadium, where he was confronted by Crennel and general manager Scott Pioli. The two of them said they never felt in danger, and that Belcher thanked them for all they'd done for him. As police arrived, Belcher slipped behind a car and put the gun to his head.

Nobody from the Chiefs said that Belcher showed any signs of depression or other personal problems. Chiefs owner Clark Hunt spoke to team doctors and coaches and, according to him, they said Belcher had no history of concussions.

He was listed on a November 2009 injury report as limited in practice with a head injury, but he returned to the field a few days later against Oakland.

The NFL has put more emphasis on diagnosing and treating head injuries in recent years. Part of it stems from high-profile suicides involving players such as Junior Seau, and part is a response to numerous lawsuits filed against the league on behalf of players who blame head trauma for depression and other problems.

Autopsy and toxicology reports may indicate whether drugs or alcohol was involved. Those results are expected in six to eight weeks.

Belcher was never a star on the Chiefs though he played enough so that he was well known around town. He was seen at concerts, and both he and Perkins did volunteer work in the community.

He was an accomplished wrestler who played offense and defense at West Babylon (N.Y.) High School, and chose to attend the University of Maine. The university said Belcher bloodied an arm after ``reportedly'' putting it through a window in 2006, an incident referred to school officials for "disorderly conduct and restitution.'' A former teammate, Mike Brusko, told the Bangor Daily News he blamed the incident on alcohol.

Family was of the utmost importance to Belcher, friends and former teammates said, and it was little surprise to anyone that he graduated with a degree in childhood development.

``I used to ask him questions about everything, and he always told me the funniest things,'' said Jerron McMillian, a safety for the Green Bay Packers and Belcher's teammate at Maine.

``He laughed a lot,'' McMillian said, ``but he was always serious about his work. He'll play with you, but when it's time to work, he's tuned in, he's focused, and he's really emotional about how he does things.''

Only a small percentage of undrafted players make it in the NFL, but Belcher managed to beat the odds. At one point during his initial training camp, Pioli told members of the Chiefs' front office, ``I really like this guy. I really think this guy can be a player.''

He wound up playing in all 16 games as a rookie, even starting three times at linebacker. He became a full-time starter in 2010, when the Chiefs won a surprising AFC West championship.

His base salary this past season was more than $1.9 million.

``He overcame a lot of things - position changes, small school. He overcame all those things through the force of his indomitable spirit,'' said Dwayne Wilmot, who coached Belcher at Maine and remained in touch over the years. ``He lit up when he spoke about his mom, or hugged his family after games. His love for them fueled him to reach the heights he was able to reach.''

Belcher met Perkins through Chiefs running back Jamaal Charles and his wife, Whitney, a cousin of the slain woman. Perkins was active in the Chiefs' women's organization, and the two of them recently had a baby girl.

``I was so excited when he became a father,'' Wilmot told the AP in a phone interview, ``because he would be a great father.''

Kansas City police said Belcher and Perkins had been arguing recently, and a friend of the couple, Brianne York, said the root of the argument was that Belcher ``sometimes he would just be down in his man cave or whatever,'' and Perkins wanted to spend more time as a family.

Other friends said Perkins was out late at a concert before their final argument took place.

``It doesn't seem that that would be the end of their story,'' York said. ``It just seems like if things didn't work out, they would have gone their separate ways.''

The reality is that nobody may ever know exactly what happened in those final hours, minutes, seconds.

``I think what we try to do is explain the unexplainable,'' said Chiefs linebacker Andy Studebaker, who was close to Perkins as well. ``This is such an unexplainable event that I don't think we could easily get through it with a single-sentence explanation.''

Unexplainable, and with devastated families left behind.

``I was once told the hardest thing a person can go through is burying their child, so my heart goes out to their families - Kasandra's and Jovan's families,'' Johnson said. ``You can just imagine what they're going through right now, and as a team, we lost a brother. It's going to take time, but life goes on.''

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Associated Press Writers Heather Hollingsworth and Nancy Armour contributed to this report.