Why did he end it? no one else is?

If a guy breaks up with a girl after a year but doesn't give a reason as to why... he just said he wasn't feeling it- a few weeks after saying he couldn't imagine his life without her. He spoke with an ex, there's no chance of them getting together and there is no one else involved.
What could be the reason? He is v. commitment scared and seems to go one step forward, ten back. This girl been there for him through the toughest few months of his life.
If he has done it in haste (he is stubborn) how long would it take him to get in touch? He knows he has deeply upset this girl. He said he just wanted her to be happy despite her been happy with him. He was pretty adamant that it was done but things did get heated. However he has done this before and come back stating the I miss you routine but he has never denied the connection between them. This time he's said there's no longer a connection but the girl disagrees. He hasn't unfriended her on face book and he has arranged to meet the one mutual friend he confided in about them, literally a week after he ended it. Could just be a coincidence but looks a bit convenient. The mutual friend works with the girl too. Just doesn't make sense. They were close friends for a good few years and then together romantically for a year with a 2 month gap in the middle. He said he only got back with her because of the negative vibes however everyone else moaned about his negativity rather then hers (they used to work together). He does have a lot going on and to be honest they do make a good couple the majority of the time. Its his first adult relationship so he could be scared but she is one of the sweetest most genuine girls that lives. I really feel for her, as she is heart broken. She doesn't understand why he would do this. So many people are mad with him. She just feels used despite knowing there were genuine feelings there. Do guys ever try to reconnect with their ex after ending it? How soon after?
Why did he end it? no one else is?
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