From Forbes:

Not all IRS agents are armed, of course. It’s only the Criminal Investigation Division, and they arguably need them. Yet even within that group there’s been some criticism. According to one government audit, IRS Agents ‘Accidentally’ Discharged Guns 11 Times between 2009 and 2011.

Some resulted in property damage or personal injury, claimed the report. What’s more, agents accidentally fired their guns more times than they did intentionally, said the Treasury Inspector General for Tax Administration. That would be a worry for any law enforcement agency.