CHICAGO (WLS) -- Two people are in custody after 13 were shot, including a 16-year-old boy, near a residence in Englewood on the South Side early Sunday morning, Chicago police said.

According to police, officers responded to the 5700 block of South May Street after Shotspotter Technology alerted them of shots fired around 12:30 a.m.

"I was awoken by the sound of, seemed like 4, 5, or 6 gunshots and it seemed pretty loud, so it seemed kind of close," neighbor Terrence Daniely said. "I didn't see any commotion when I looked out the window but then shortly after I heard the sounds of people screaming and running from a party on the street."

"It was just so many people out, so many cars on the street, and the police response was amazing, it seemed like there were 100 police officers running to the scene," Daniely said.

Chicago police said the shooting occurred at a gathering to celebrate the birthday of a 22-year-old man who was shot and killed in April while attempting a carjacking the South Loop. He was shot by a 41-year-old concealed carry license holder, who police say was the victim.

Before the gunfire erupted overnight inside the home, police said there was some sort of dispute.

Police said shots were initially fired inside a residence, and then people started to flee outside into the street.

"People started to spill out. As they started to spill out, more shots were fired," said Chicago Police Chief of Patrol Fred Waller. "We saw an individual on the POD firing and at that time shots were fired at another location."

Waller said POD cameras helped officers get information about what transpired.

"POD videos shows who was firing outside so we have some information about what happened there," said Waller. "One of the people who left the party also fired shots at a passing vehicle so we have about three different crime scenes to cover."

According to Waller, seven people were transported with gunshot wounds from the scene and six others transported themselves.

A 16-year-old boy was taken to an area hospital in critical condition but has since been stabilized, Waller said.

Four others are still in critical condition, police said. The victims' ages are between 16 and 48.

Police confirmed two people are in custody and being questioned regarding the incident.

One suspect was arrested at the scene with a revolver, Waller said. An unidentified person who was shot during the altercation and initially transported to a hospital is also being questioned as a suspect, Waller said.

WATCH: CPD Chief of Patrol Fred Waller gives update on mass shooting at Englewood house party

CPD said they plan to increase police presence in the area.

Mayor Lori Lightfoot visited the injured at University of Chicago Hospital early Sunday.

"One of the victims inside specifically said to me, 'I just want to know who did this,'" Lightfoot said. "I want to make sure they're brought to justice and that is the commitment we are making."

The mayor also visited Canaan Community Church in Englewood for Sunday service to try to calm community concerns.

"I am praying for every member of every family that was affected today," said Jonathan Brooks, the church's senior pastor. "We know the violence doesn't just hit the actual victim but every person connected to that victim."

Illinois Gov. JB Pritzker said on Twitter that he's offered support and resources to Lightfoot and Alderman Stephanie Coleman, of the 16th Ward.

Pritzker said, "I'm outraged and devastated by last night's shooting. Our communities and our children should not have to endure these unspeakable tragedies and my heart goes out to the people of Englewood."

Ald. Coleman said the shooting is not representative of the neighborhood and she's saddened by the violence over Christmas break.

"Very sad and very disappointed that our children, this is their welcoming not only into the Christmas holiday, but to their Christmas break," Coleman said. "I saw disappointment. I saw frustration. I saw fear. I saw lots of concerned neighbors getting to the bottom of it. I saw children at 12:30 in the morning, could you only imagine children out because there was that much activity going on."

WATCH: 16th Ward Alderman Stephanie Coleman speaks on Englewood mass shooting

Area South Detectives are currently investigating.

This shooting brings the weekend violence total to 33 shot, four fatally, across Chicago since Friday evening.