A mass shooting killed four people and wounded 18 others in a popular nightlife area in Birmingham, Alabama, with many of the victims caught in the crossfire, police said early Sunday. No one was immediately arrested, and police asked the public for information. The shooting happened shortly after 11 p.m. Saturday in the city’s Five Points South entertainment district, Officer Truman Fitzgerald said in an email. Officers arriving at the scene found two men and a woman on a sidewalk with gunshot wounds, and they were pronounced dead there. An additional male gunshot victim was pronounced dead a…