( CNN ) -- A man coolly and calmly approached the screening area outside the Pentagon Thursday evening and opened fire , grazing two Pentagon police officers before they returned fire , critically wounding him , officials said . The incident happened at 6:40 p.m. , when the man wearing a coat -- with `` no real emotion in his face '' -- approached the officers outside the Pentagon Metro station , said Pentagon Police Chief Richard S. Keevill . `` As the officers started to ask him for his pass to get into the Pentagon , he drew a weapon from his pocket and started shooting immediately at the officers '' from a few feet away , Keevill told reporters . `` He drew a gun and just started shooting immediately . '' The two Pentagon Force Protection Agency officers returned fire with their semi-automatic Glock .40-caliber weapons and the suspect , thought to be a U.S. citizen , was critically wounded , Keevill said . He praised the police officers for acting `` quickly and decisively to neutralize him as a threat '' without hurting anyone else . Asked how many shots were fired , he said , `` Many . '' Keevill would not identify the man . The Pentagon Force Protection Agency is the Pentagon 's police department . Pentagon entrances were locked briefly but all were reopened with the exception of the Pentagon Metro entrance , the Pentagon said in a statement . Lisa McDonald , a spokeswoman for George Washington Hospital , said three people were being treated there -- both officers and the suspect . The Pentagon police department , the Arlington County Police Department , U.S. Secret Service and the FBI were all involved in the investigation , Keevill said . The Pentagon is one of the largest office buildings in the world with three times the floor space of New York 's Empire State Building , according to its official Web site . Some 23,000 military and civilian employees work there . Are you there ? Send images , video . Though it contains 17.5 miles of corridors , a person can walk between any two points in the World War II-era building in no more than seven minutes . CNN 's Mike Ahlers , Larry Shaughnessy and Jeanne Meserve contributed to this story .
NEW : Suspect shot at officers at Pentagon screening area , police said . NEW : Suspect was injured in return fire from two officers . Pentagon police say one person is in custody . Three people being treated at George Washington Hospital .