One person was killed and three others hospitalized in a shooting at a medical building in Atlanta on Wednesday, police said in a tweet, and a suspect is still at large.

Police responded to an active shooter just after 12:30 p.m. local time in the midtown section of the city, the Atlanta Police Department said in a tweet.

“Anyone in the area is asked to secure their building and shelter in place. Anyone not in the area is asked to stay away,” the department said in a separate tweet.

Atlanta police posted four photographs of the suspect, who appeared to walk into an office doorway and raise his arm. The suspect had a mask over his face and nose and was wearing a sweatshirt and a brown backpack.