Our V has started a new (frightening) behaviour - he jumps at the person walking with the lead and bites them when they do not do what he wants (walk in the direction he wants to go). He bites hard, with growling and has started to draw blood. This behaviour is brought on suddenly (it has been occurring for about 6 months and getting progressively worse). He walks well on the leash and without notice or provocation, he will start to use his front feet to "crawl" up the leash and immediately go for the hands holding the leash. If that does not work, he will jump on the person and try to bite their hands or anything he can get a hold of. Often showing teeth and growling. He only does this when on the short lead. There is never any dogs or other people around - he usually stops when someone approaches (because he is distracted). Once the person moves on, he is back at it. It can take 2-3 minutes to settled him down - usually talking quietly and trying to get him to sit (very difficult to do when he is biting hard). Once he is sitting and had a minute or two to settle he is perfectly fine to continue on the walk. At one point a police office stopped while driving by to ask if we were ok (he was worried about the dog attacking us). We explained that it is just something he does and the officer continued on his way. We have tried stepping on the leash, holding him, distracting him, keep walking, etc. but nothing works - it is like a switch goes off in his head and he goes crazy. He is getting more aggressive (biting harder) as time goes by. We are at our wits end on how to address this problem. We were using a pinch collar and switched to an easy walk harness (thinking the pinch collar triggers his behaviour) - that did not change anything. Otherwise he is fine in the house, outside, etc. We read that this might be a behavioural issue and we would need to see a trainer specializing in behavioural issues. We are very concern about this behaviour. Will we need to put him down? Comments?