My dog died

Smokey our black lab that we have had for 13 years died on Thursday. I was not at home when it happened, but it was pretty dramatic occurrence. He has been an amazing dog. We found out a few weeks ago that he had cancer, but he has not appeared to suffer at all so we were going to keep him alive until he appeared to be in pain. Thursday morning he went outside like normal and came back in and fell down. He then tried to crawl across the floor like he was in major pain. He finally was able to stand up and couldn't sit back down. My mom was calling everyone to come home. My mom then saw that Smokey went outside to go to the bathroom and he did not come when she called. My mom and sister Kelly found him laying in the ground unable to move. They were able to get him inside and he just lay on his bed. A few minutes later he was gone.
There was no dog like Smokey. Everybody loved him. All the neighbors knew him and would give him treats. Smokey never barked, would jump on people, go on any furniture and he also knew what rooms he was not allowed in and never went in the rooms. Smokey could sit, lay down, and jump up for treats. Smokey was the best dog.