Police are looking for a suspect who used a boat to access a Tennessee Valley Authority nuclear power plant Sunday morning and exchanged fire with a security guard on the plant grounds before fleeing downriver.

The shootout occurred "several hundred yards from the site’s protected area, which houses the reactor and power production facilities," TVA spokesman Jim Hopson said in a press release.

A security guard on routine rounds reportedly spotted the suspect leaving his boat and walking ashore about 2 a.m. When the guard advanced to question the suspect, the lone man began shooting. The guard returned fire and called for backup. The suspect then "sped away on his boat," according to a local news report.

Authorities labeled the shootout an "unusual event," the Nuclear Regulatory Commission's lowest emergency classification.

Opened in 1996, Watts Bar is in southeastern Tennessee between Chattanooga and Knoxville. Nearly 1.2 million people live within a 50-mile radius of the plant, and population growth since 2000 has been rapid.

There was never any immediate danger to the plant's reactor, and it's not clear how much damage a lone gunner could actually do to a complex like Watts Bar. Coincidentally, federal authorities just ran their first-ever nuclear terrorism drill last Tuesday at Three Mile Island in Pennsylvania. In that simulation, a team of eight gunmen attempted to take over the plant; government spokesmen would only say publicly that that the plant's response was "adequate."

[WBIR; Image via AP]