Gunman killed after dramatic shootout with authorities outside US courthouse

The FBI is investigating the military background of a gunman who opened fire outside a US courthouse, sparking a shootout with police.

Armed with a rifle and wearing tactical gear, the suspect was taken down by authorities before he entered the building.

According to the FBI, the man died after being shot in an exchange of gunfire with officers outside the courthouse in downtown Dallas, Texas.

More than 200 FBI agents are now working to determine the suspect's motive.