ORIGINAL POST 3:36 PM: There's not much information at the moment:

An FBI spokesperson in Texas confirms that there was a shooting on Fort Hood military base.

Fort Hood officials sent out a tweet asking all personnel to shelter in place. Everyone has been advised to close doors and stay away from windows. All students and personnel at Central Texas College have been ordered to immediately evacuate the central campus. The college has cancelled classes for the rest of the day.

The suspect is reportedly still at large. In 2009, Fort Hood was the site of the deadliest shooting spree to ever take place on an American military base. This post will be updated as more news comes in.

UPDATE 3:57 PM: Fort Hood officials are being smart about not releasing too much information to the media. At present, all we know is that this is an active situation. You'd be wise to ignore reports of multiple gunmen, or to focus too much on eyewitness reports. The scene is undoubtedly chaotic there, and witnesses are unreliable in chaotic situations. We'll be keeping an eye out for official reports, and updating accordingly.

UPDATE 4:32 PM: Still waiting for official confirmation. The AP is reporting numbers, citing a senior official:

UPDATE 4:38 PM: An update from Fort Hood begins, "Fort Hood's Directorate of Emergency Services has an initial report that a shooter is dead but this is unconfirmed." They also don't confirm the number of injured and state that Fort Hood is still on lockdown.

UPDATE 4:43 PM: From the AP and, again, not confirmed by Fort Hood:

UPDATE 4:51 PM: President Obama says he's following the shooting and promises to figure out what happened.

UPDATE 5:53 PM: Officials at Scott & White Hospital say they're tending to four shooting victims, and that two more are on the way, with conditions ranging from stable to critical.

UPDATE 7:11 PM: The lockdown has been lifted at Fort Hood. Four people are dead, the Washington Post reports:

A shooting at the Fort Hood military installation in Texas left at least four people dead, including the gunman, and more than a dozen were injured, according to authorities.

The gunman, identified by multiple government sources as Army Specialist Ivan Lopez, took his own life, officials said.