Two teenagers were killed and three other people were injured when gunfire erupted inside a crowded Houston “pop-up party” police said was organized via social media.

The Saturday night shooting unfolded at a strip mall in North Houston, where an empty storefront was illegally converted into a “makeshift club” packed with juveniles, Assistant Chief Luis Menendez-Sierra said during a news conference early Sunday.

Officers answering a shooting-in-progress call at 11:20 p.m. local time found a “very hectic scene” with a large crowd of people running out of the makeshift club, Menendez-Sierra said.

“It’s kind of one of these last-minute parties, pop-up parties that have been popping up lately,” Menendez-Sierra said.

A 16-year-old boy died from a gunshot wound at the scene and a 16-year-old girl hit by gunfire was taken to Texas Children’s Hospital in Houston, where she was pronounced dead, police said.

A 13-year-old girl wounded in the shooting was in critical condition at Texas Children’s Hospital, Menendez-Sierra said. He said two other people, including a 19-year-old, were also injured.

“We lost some young people tonight that was very preventable if they didn’t come to locations such as this,” Houston Mayor John Whitmire said at the news conference.

Menendez-Sierra said no suspects had been identified and asked for witnesses who attended the pop-up party to contact police investigators.

Menendez-Sierra said the majority of those attending the party were juveniles.

“We are assuring the public that we are going to put all our resources into finding out what happened here tonight and who did this so we can bring them to justice,” Menendez-Sierra said.

He said the shooting stemmed from a recent trend of people quickly organizing last-minute parties on social media. He said the shooting Saturday night occurred in an empty business that had been leased out.

“Since they’re not under any regulations, which is what causes the problems with these types of events with no regulations, there’s nothing guarding it,” Menendez-Sierra said.