St. Petersburg police are investigating after a man was stabbed to death Friday evening outside a downtown sushi restaurant. Officers responded just before 6 p.m. to 364 1st Avenue North, outside of Ahi Sushi. Police said a man was stabbed during an altercation outside the restaurant and died a short time later at the hospital. Officers are questioning two men to find out what led to the stabbing. First Avenue North is closed between 3rd and 4th streets for the ongoing investigation.