At least four people were wounded Thursday in citywide shootings over a 24-hour period.

The last reported shooting wounded a 19-year-old sitting on top of a vehicle in the East Chatham neighborhood on the South Side.

Another vehicle drove by at 4:16 p.m. and someone inside fired shots, striking the 19-year-old in the lower left abdomen, according to Chicago police.

The man was taken from the 8200 block of South Ingleside Avenue to the University of Chicago Medical Center in good condition, police said.

Another man was shot and seriously wounded during an argument in an alley in the South Side Park Manor neighborhood.

A 25-year-old man was arguing with someone about 3:30 p.m. in the 7000 block of South Wabash Avenue when other people approached in a dark-colored car, stepped out and opened fire, according to police.

He was shot in he shoulder and taken to the University of Chicago Medical Center, where he was in serious condition, police said.

The first reported shooting involved a man and a woman wounded by someone dressed as a mail carrier in Fernwood on the Far South Side.

The man, 27, and woman, 23, were inside a home at 2:18 p.m. in the 9900 block of South State when “an unknown offender dressed up as a mailman” knocked on the door and said he had a package for the man, according to police.

When the man opened the door, the suspect opened fire, striking both victims, police said. They were both taken to Christ Medical Center in Oak Lawn.

The man suffered multiple gunshot wounds to the chest and was listed in serious condition, police said. The woman was shot in “the lower body” and her condition was stabilized.

No one was in custody Thursday afternoon as Area South detectives investigated.