jeff zellany, reporting from the capitol, from his post. some images coming in in addition to what you're looking at right there. you can see a sniper on the capitol grounds. a very tense afternoon unfolding on capitol hill. and a notice went out from the capitol police advising everyone by email. this is the notice, to close, lock and stay away from external doors and windows. the notice says that gunshots have been reported on capitol hill there are unconfirmed reports of an officer injured as you heard from jeff zellany a short time ago. i want to bring in our senior justice correspondent, pierre thomas who joins us on the telephone. this is a quick-moving investigation, pierre. >> that's right, david. we just heard from law enforcement sources. we're being told that the fbi, atf and all law enforcement officers are responding to the capit capitol. based on reports of a car chase and shots fired. we also are getting some guidance from sources that a suspect may have been shot. and may be neutralized at the scene. we're trying to get addi