Tracking Down a Problem User
Apart from sp_whoisactive as mentioned in earlier answer, i can suggest running extended events for the type of query you want to track.

You can use the events and action as mentioned in the log Tracing Query Performance with Extended Events

I really like the extended events for the amount of data you can capture out and its not that expensive depending upon how much you capture.

Additionally you can use sp_blitzwho Forget sp_Who and sp_Who2:
sp_BlitzWho tells you what’s really happening.