A retired construction worker shot five neighbors in his Chicago apartment building Saturday — killing four while they were sitting at the dinner table, according to new reports.

Police said the 67-year-old gunman, who has not been identified, walked into a neighbor’s apartment on West Irving Park Road in Northwest Side and opened fire, killing all four people, WGN-TV reported.

“When he walked into that neighbor’s apartment, there were four people at the table eating dinner,” First Deputy Superintendent Anthony Riccio told the station. “For reasons we don’t yet know, he opened fire and killed them.”

He then went upstairs and shot a woman — who was later listed in critical condition at a local hospital.

Chicago Mayor Lori Lightfoot called the shootings “devastating and almost unfathomable” in a Twitter post on Saturday.

Residents in the building told police the alleged gunman knew his victims and has had issues with neighbors before. They said the man has “anger problems.”

The alleged shooter was taken into custody at the scene and a gun was recovered, the paper said.