Police vehicle file photo. (Michael Izquierdo / WTTW News)

A 16-year-old boy has been charged as an adult in a triple homicide that occurred in Chatham last month.

The teen is accused of pulling out a gun and opening fire following an altercation inside a home in the 8000 block of South Vincennes Avenue on Feb. 25, according to Chicago Police Department Chief of Detectives Antoinette Ursitti, who spoke at a news conference Thursday.

Three people were fatally shot: two men, ages 20 and 36, and a 14-year-old boy. A 16-year-old boy was also shot and seriously wounded, Ursitti said.

The 16-year-old defendant, whose name is not being released because he is a minor, faces three counts of first-degree murder and one count of attempted first-degree murder.

He was slated to appear in bond court Thursday.

Ursitti said several additional people were inside the Chatham home at the time of the shooting; the alleged gunman ran away and was captured on video. U.S. marshals arrested him Tuesday at a relative’s home in south suburban Hazel Crest following an investigation, authorities said.

“In just a few moments, he forever changed the lives of surviving victims and those he killed,” Chicago police Supt. Larry Snelling said Thursday. “He has to be held accountable. Period. That simple. There is no excuse for anyone to reach this level of violence.”

No additional details about the shooting were immediately available Thursday, but Ursitti did say the defendant had been welcomed inside the Chatham home as an acquaintance of a friend of the family who lived there.

In announcing the charges Thursday, Cook County State’s Attorney Kim Foxx offered condolences to the families of both the victims and the alleged gunman “for yet another tragedy that has rocked our community.”

“To the family of the accused: I recognize the immense pain you must be experiencing,” Foxx said. “Your lives, too, have been forever changed and altered by this tragedy of what should have been a young boy who acted … as a man and will suffer the consequences as an adult. Our commitment to justice is unwavering, but justice alone cannot heal the deep-seated issues that contribute to these tragic outcomes.”

Ald. William Hall (6th Ward) called on Chicago communities to work together to reduce violence.

“Until we get to the day where we build communities, we won’t save lives,” Hall said. “Until we build schools, parks where kids can go, we will continue to lose lives whether it’s by a gun or by a jail cell. So the question now becomes: How can we build together so that we can work alongside our police, work alongside our state’s attorney to save lives? … I’m calling everyone, before it gets hot, before the summertime comes, what block will you build on? What life are you going to serve and save so that we don’t lose another child to a grave or a jail cell?”