MANILA- The Senate is set to investigate the death of University of Santo Tomas (UST) law freshman Horacio Castillo III, who was killed in an apparent hazing incident that has revived calls to strengthen the law against violent fraternity initiation rites.

Sen. Panfilo Lacson, chair of the Senate committee on public order and dangerous drugs, set the hearing on Monday following an impassioned privilege speech by Sen. Juan Miguel Zubiri.

In his speech, Zubiri, a long-time classmate of the victim's father, called for the passage of a new law that would ban hazing outright and provide stronger penalties against those who participate in the act.

The senator argued that the current anti-hazing law only "regulates" hazing.

Castillo, 22, died of a heart attack after sustaining "massive" injuries consistent with hazing, a police autopsy found. His parents learned of his death before dawn Monday, after he was brought to the Chinese General Hospital and declared dead upon arrival Sunday.

His body was initially reported to have been found bloodied and bruised on a sidewalk in Balut, Tondo, Sunday by one John Paul Solano. The latter is now a primary suspect in the killing.

• READ: 'Barbaric': Family of UST student killed in hazing cries for justice

Sen. Chiz Escudero said he wants UST Civil Law dean Nilo Divina to appear on Monday's hearing.

Zubiri called on Divina as well as other members of the UST Faculty of Civil Law who are members of the Aegis Jvris fraternity to cooperate in the investigation.

"I challenge dean Divina and other faculty members of the UST Faculty of Law to cooperate in the investigation and to tell all that they know about the incident," Zubiri said.

"No wonder the culture of violence never ends in our country as those who swear an oath to defend our laws are the very same ones who commit the violence," he added.

The Aegis Jvris fraternity had earlier vowed cooperation with the investigation into its alleged involvement in the fatal hazing.

• READ: UST student was sole hazing target: Zubiri

Sen. Joel Villanueva, a UST alumnus, said Castillo's death "has shaken me to my very core" as he condemned the "senseless act of violence."

"As a UST alumnus, I urge my alma mater and the proper authorities to investigate and hold the people accountable for this unfortunate incident involving Atio, my fellow Thomasian," Villanueva said in his manifestation supporting Zubiri's probe call.

"No type of brotherhood can ever equate to the sanctity of life. Hinding-hindi nasusukat sa karahasan ang tunay na kapatiran," he said.

Sen. Sherwin Gatchalian meanwhile recalled how a similar incident in 2014- the hazing death of De La Salle College of St. Benilde student Guillio Servando - had prompted moves to strengthen the law against violent initiation rites.

He said a proposal passed the House of Representatives, of which he was a member at the time, but that the measure failed to reach the Senate "due to lack of time."

• READ:Senate body asked to set hearing on hazing bill

"Mr. President, taon-taon na lang mayroon tayong nakikita at naririnig na ganitong pagpaslang ng buhay, lalong-lalo na ng mga estudyante," Gatchalian said in his manifestation.

"And every time that there is such a story, we would see a lot of support and a call for a new law. It’s really about time to look at this incident and to really come up with a clearer and stringent law," he said.

An incensed Sen. Manny Pacquiao also condemned the incident, calling Castillo’s killers “cowards.”

“Kung hindi lang masama, Mr. President, puwede ko silang hamunin. Hindi. Sabay-sabay,” he said in plenary session.

“Sa totoo lang, 'yun ang mga duwag na tao, 'yung mga nambubugbog ng walang kalaban-laban.”

-- with a report from Christian Esguerra, ABS-CBN News