KANSAS CITY, Kan. — One week after he had angrily barged into a small neighborhood bar, seething and belligerent, the man returned, cursing and shouting about gangs. He threw a plastic cup at a bartender who refused to serve him, witnesses said, and fought with a customer before he was escorted out, just as he had been the week before.

But two hours later, in the pre-dawn darkness of Sunday morning, he and another man stormed back in and opened fire on the crowd, the authorities and witnesses said, killing four people, wounding five others and shattering the sense of safety this tight-knit Latino community felt inside Tequila KC, a bar that for many served as an extension of their living rooms.

Both gunmen left the scene before the police arrived, and no arrests were made Sunday in connection with the attack, which occurred shortly before 1:30 a.m. and sent dozens of panicked patrons into the street.

Hours later, traces of blood remained on the sidewalk.

“This is a community bar,” said Jose Valdez, 39, who was working as a bartender when the shots began. “Here, everybody knows everybody.”