The attack in Boulder ended with police detaining an injured, shirtless suspect at the King Soopers market. Police arrested a suspect, but didn’t reveal his name or any details about the shooting at an evening news conference. Boulder police Chief Maris Herold said the investigation may take five days.

The attack was the seventh mass killing this year in the US, following the March 16 shooting that left eight people including 6 Asians dead in Atlanta. The shooting has evoked protests against violence and discrimination against Asians around the US.