I'm sorry to hear about the dog Don, these animals need to be carefully watched even when they have been in a home environment for a period of time. They never lose the chasing instinct and it gets them into lots of trouble in the world of humans.

Best thing is to get another as soon as possible, but I never allow my dogs off the leash unless I am certain they are in a secure and safe area....they are a little short in the brain dept and have absolutely no fear of injury, the red mist descends.
A greyhound of about five years old is more placid and makes an excellent companion

They are not "pets", as they are slightly detached and don't like a lot of fuss, but have a sort of nobility which I always think has to do with antiquity of the breed. They were kept by the ancient Egyptians as hunting dogs and were deified in legend.