Here's the completed text with the verbs in the correct tense (Past Simple or Past Continuous):
I was walking (walk) home when I saw (see) Uncle George in his car. He was turning (turn) right when a tired hungry dog ran (run) into the road. Luckily, Uncle George was driving (drive) slowly when the dog went (go) in front of his car and he stopped. Now Rex lives with Uncle George!
Uncle George loves Rex and Rex loves Uncle George.
Explanation of Tenses Used: