Do you think that maybe they wanted to first remove him from an environment with other people, co-workers for example, and surrounds of which he was familiar and had the potential to cause violence or react unpredictably?
Taking him by surprise at the police station might be safer? As he wouldn't be expecting it, or prepared. Nor would it be a familiar environment to him, unlike his work place where he has the capacity to reach for a saw or metal bar for instance and try and attack someone if he freaked out. Mechanic's workshop would have lots of potentially dangerous equipment lying around. Just a thought.
Hit the nail on the head there I reckon. Or the cops could have been worried that by the time they got back to the Police Station which was 20 minutes away, it would be totally surrounded by hundreds of not-so happy locals ready for a game of baseball or cricket, with the young thugs head, and wanting to gut him like the slimy little fish that he appears to be.