yard in washington again today. it's still an active crime scene. two days after aaron alexis walked into the building, building 197, and killed 12 people. but now we have a better idea of how an armed man got inside and the shooting battle with police that lasted more than an a half hour. cnn's evan perez joins us from washington with more on that. good morning. >> good morning, carol. the scene inside the navy yard this morning is the fbi is still there trying to catalog everything that went down, including all the shots fired. we now know the authorities tell us that this was a gun battle that lasted well over 30 minutes. apparently the suspect, aaron alexis, entered the washington navy yard with a small bag. he apparently had it in his car. he got into the building with his pass, went up to the fourth