A look back at Baruch College student's hazing death

— -- Four former fraternity members from New York City's Baruch College pleaded guilty Monday to voluntary manslaughter for their roles in the hazing death of pledge Chun "Michael" Deng.

Deng, a 19-year-old Baruch College freshman, was pledging the Pi Delta Psi fraternity in 2013 when he died after a hazing ritual at a home the fraternity rented in Pennsylvania's Pocono Mountains.

The Pocono Mountain Regional Police Department said Deng was injured while participating in a ritual called the "glass ceiling," in which pledges, blindfolded and wearing a 30-pound backpack, must "get through a line of brothers while fraternity members shove and take the pledges down and resist the pledge from getting through the line."

Police said "Deng was [tackled] and then was complaining about his head hurting. Deng was eventually knocked out ... Deng was then carried inside unconscious. It was reported that Deng was having trouble breathing."

Authorities said fraternity members called the national fraternity president, who allegedly told them to hide all fraternity items. Police said that during that time some members changed Deng's clothing and conducted internet searches for phrases like, "concussion can't wake up."

The students waited more than an hour before driving Deng to a hospital 45 minutes away, police said.

Deng suffered trauma to the head, torso and thighs, a forensic pathologist said, according to police. The 19-year-old died from multiple traumatic injuries and "the delay in treatment of 1-2 hours significantly contributed" to his death, the forensic pathologist said.

"He suffered a serious head injury and it was clear he needed to go to the hospital," Deng family attorney Doug Fierberg told ABC News Monday. "He needed emergency attention and they delayed for several hours... and during that time, Michael’s opportunity to survive was extinguished."

Jim Swetz, the defense attorney for one of the defendants who pleaded guilty Monday, said his client has accepted responsibility. But Swetz also said this was not an intentional act of violence.

"This was not an intentional act. This is a tragedy for all concerned," Swetz told ABC News Monday, adding, "We recognize the tragedy to the Deng family."

The four defendants who pleaded guilty to felony manslaughter and hindering apprehension charges Monday had been charged with third-degree murder. Sentencing is set for December and they face 22 to 36 months in prison, The Associated Press reported.

Dozens of other people are facing less serious charges and the fraternity itself was charged with murder, the AP said.

The Associated Press contributed to this report.

ABC News' Gio Benitez, Shah Rahmanzadeh and Faryn Shiro contributed to this report.