The Fremont, California, man had spied his 75-year-old neighbor named Richard Dubiel on his roof. Alarmed, David approached him.
The senior needed to replace his shingles and had been doing the work all by himself. David admitted feeling incredibly sorry for the man and wanted to help him, but didn't know how to patch a roof, he told ABC News.
"Seeing his age, I just felt that he shouldn't be doing this by himself -- for safety reasons and I just felt sorry for him. That's when I decided to reach out on social media to see what kind of response I'd get."
So David posted on Facebook to see if anyone with roofing experience would donate their personal time to help Richard. It was a little nerve-wracking watching the elderly man clamber around on his roof and all he needed was a little bit more manpower.
David wrote on Facebook:
"I feel sorry for him but I have no roofing skills. I would like to see if anyone can donate their time to help him finish. It appears that he has all the materials so looking for free labor to show up..."
He had no idea if anyone out there would be willing to help - but decided it would be worth a try just to ask.
David's one simple post ended up being shared 1,400 times! Approximately 40 people offered to help Richard, which was amazing.
He told ABC News:
"I was astonished. I was so surprised and delighted because I was not expecting such a response. You see so much negativity and out here, this was positive--real positive with no thought of return or reward, other than that of helping somebody."
Others volunteered to donate water, pizza and doughnuts to the cause. David anticipated the project taking all day, but with that many people volunteering, they were done in less than half that time.
"I thought it was going to be a full-day's work, but with the amount of people and experiences, I'd say it took just four hours. I think he was still kind of in awe or in shock since he's used to doing things by himself. He was definitely grateful and thanked everyone for all their hard work."