Police say a Kalamazoo man was arrested yesterday after breaking into a house to threaten his ex-girlfriend with a knife.  It happened on Bronson Avenue at around 2:30 in the afternoon.  Investigators say the suspect tracked his ex to her friend’s home and began to argue with her and then attacked and choked her.  Witnesses told police the woman ran into the house to escape but the man forced his way in and pulled a knife, but fled when he heard the police were coming.  The man was caught a few blocks away and the knife was found on the ground nearby.