Should this deputy sheriff have been arrested by me?

We had many riding mowers stolen this one summer. Not the cheap mowers, but the high-dollar ones. I finally arrested three suspects for the thefts and they began to tell me which people had bought these stolen riding mowers. One was a deputy sheriff. I drove to his house and walked the fence line, next door, down to a big dog house in his backyard. Fortunately, the stolen riding mower was there and I was able to retrieve the serial number, without entering his property. It was in plain view. I secured a search warrant and served it on the deputy. I recovered the stolen riding mower and turned it over to its owner. I did not arrest this deputy. I turned this information over to internal affairs for his sheriff department. Their investigation led to his termination and arrest for concealing stolen property. Question: I have always wondered if I made the correct decision to not arrest this man myself, instead of letting internal affairs handling it. What do you think?