A memorial for a Chicago man shot dead earlier this year turned into a bloodbath early Sunday with at least 13 people getting shot, according to authorities.

The house party just days before Christmas was to honor the birthday of Lonell Irvin, a 22-year-old man fatally shot during an attempted carjacking in April, sources told the Chicago Tribune.

At least two gunmen are believed to have opened fire just after 12:30 a.m. with at least four victims — including a 16-year-old boy — left in critical condition, police said.

The victims range in age between 16 and 48 and suffered “different and various gunshot wounds to their bodies,” Chicago police Chief of Patrol Fred Waller said.

The shooting started inside following a dispute inside the South Side house, with more shots fired as people fled for their lives — with police saying more than one gunman was involved.

“Definitely there was two different shooters,” Waller said, according to the Tribune. “It looked like they were just shooting randomly at people as they exited the party.”

Two people are being questioned, Waller said, with at least one arrested with a weapon. Another was one of the 13 wounded, he said.

Police recovered a revolver and called the carnage an “isolated incident.”

The irony of more gun violence at an event mourning the loss from such an attack was not lost on those who were there.

“It was his birthday and they were just celebrating a memorial for somebody that passed away, and this is what they do,” a 29-year-old woman who declined to give her name told the Tribune.

“It’s real f–king sad. Your kids can’t grow up, you can’t do nothing. This is what our life is going to be about.”

With Post wires