Tension erupted at a Senate hearing on extrajudicial killings Monday evening after a senator accused another lawmaker of concealing vital information about a self-confessed member of the Davao Death Squad..

The debate during a joint hearing of the Senate committees on justice and human rights and public order and dangerous drugs, which began around 9 am and ended before 11 pm, when Senator Richard Gordon accused Senator Leila De Lima of "material concealment."

National Bureau of Investigation officers revealed during the hearing that Edgar Matobato had a kidnapping case against him in connection with alleged terrorist Sali Makdum in 2000.

A fuming Gordon accused De Lima of hiding information from the Senate committee after De Lima admitted she had notes of Matobato's kidnapping case.

"This is a vital piece of information. A very critical piece of information that should have been revealed here and out of respect for Senator De Lima I said it was an oversight on her part but this is a very, almost fatal, oversight, because as Senator Lacson has pointed

out, we invited, for various reasons, the policemen," he said.

The lawmakers wanted Matobato to return to the witness stand in the evening where he would have confronted the policemen he accused of being death squad members. The policemen also denied that a death squad existed.

But Matobato left the venue.

Senator Antonio Trillanes IV explained he allowed Matobato, who is under his protective custody, to leave as traveling late at night would be dangerous.

Gordon stressed Matobato should not have left without seeking clearance from them.

"He must stay. That is the order of the chair so in case he will be needed, he will be presented. He has no business leaving the premises without telling the chair," said Gordon.

Trillanes defended De Lima from insinuations she deliberately hid the information of Matobato's kidnapping case, noting the alleged assassin admitted a kidnapping case was filed against him based on transcript of stenographic notes of the previous hearing.

Gordon disregarded the transcript, prompting De Lima to demand an apology but the former refused. A emotional De Lima then walked out of the session hall.

"And since no apology is forthcoming, I am walking out. Because clearly, there was no concealment on my part because it was disclosed already," she said. Emmanuel Tupas