According to police representatives, the attacker shot himself and his condition is unknown. The investigators are trying to establish whether there are other victims.
People in the area are encouraged to take shelter, unless otherwise instructed.
Law enforcement officers are concentrated around the UPS San Francisco facility, a couple of blocks east of Franklin Square.
As it was reported earlier, another attack occurred in Alexandria, Virginia State, during a Congressional baseball practice. Republican Steve Scalise was badly injured, but remains in stable condition. His assistant and two police officers were wounded in the attack.