Last Updated: US Capitol Attacker's Motive Still Unclear, Investigation Underway The motive of the suspect who rammed the car near the United States (US) Capitol killing one officer and injuring another, Noah Green still remains unclear. Image credits: AP The motive of the suspect who rammed the car near the US Capitol killing one officer and injuring another, Noah Green still remains unclear. On April 3 Green rammed a car into a police barricade outside the Capitol building, brandished a knife and lunged at officers. Police then shot the 25-year-old and mortally wounded him. The attack pierced the calm of a spring afternoon on Capitol Hill and caused the second-on-duty death of a US Capitol officer following the January 6 insurrection at the federal building.