WASHINGTON, April 2 -- U.S. President Barack Obama said on Wednesday that he was heartbroken on a shooting incident which occurred at the U.S. Army base of Fort Hood in Texas Wednesday afternoon.

"We're following it closely," said Obama at a Chicago restaurant.

According to the hastily arranged comments released by the White House, Obama also said the situation is "fluid" right now, and his national security team is in close contact with not just the Defense Department, but also the Federal Bureau of Investigation (FBI).

Law enforcement officials said the shooting so far has left at least four dead and more than a dozen injured.

"I want to just assure all of us that we are going to get to the bottom of exactly what happened," Obama said.

"Obviously this reopens the pain of what happened at Fort Hood five years ago," he said of another shooting rampage in 2009, which left 13 people dead and more than 30 others wounded.