Updated

The legal defense team for a U.S. Marine accused in a fatal stabbing at Camp Pendleton in California argued Thursday that the death was a tragic accident that occurred while the two friends were playing with a knife.

The prosecution countered that the defendant went off to hide the bloody knife rather than help the bleeding victim.

Pfc. Raymond W. Begay, 20, faces charges of murder and obstruction of justice in the Jan. 16 death of 18-year-old Pfc. Ethan Barclay-Weberpal.

Barclay-Weberpal, from Wisconsin, died after being stabbed while sitting in formation with a platoon of Marines at the School of Infantry at Camp Pendleton, about 40 miles north of San Diego.

Defense attorneys said Begay should be charged with involuntary manslaughter, not murder.

Several troops testified for the defense Thursday that the death was an accident, the Orange County Register reported. Begay immediately admitted to training instructors that he stabbed Barclay-Weberpal, witnesses said.

“This was just dumb kids doing dumb things,” defense witness Pfc. Rhett Glubka said. “I don’t think he (Begay) thought about what could have happened.”

“This was just dumb kids doing dumb things. I don’t think he (Begay) thought about what could have happened.”

— Pfc. Rhett Glubka, defense witness

Lance Cpl. Gavin Shorter testified that the other Marines saw blood coming from Barclay-Weberpal's chest and tried to tug at his shirt to cover it up.

"We didn't think it was fatal and we didn't want to get into trouble," Shorter said. "After we got out of formation, we were going to help him."

Shorter testified that Begay was playing with a knife before he stabbed Barclay-Weberpal.

Maj. Tanzania Jaysura, lead trial prosecutor, said she had testimony from at least three other Marines who said Begay was known to have threatened to stab other Marines and that some had told him to stop because it made them uncomfortable.

She said she also had testimony showing Begay left the bleacher area after the stabbing to wash blood from his knife.

"The knife was not the type of knife that retracts and opens to the front and witnesses will say they saw him play with the knife before the stabbing and that words were exchanged and that he intentionally put the knife into Barclay-Weberpal's left chest, into his heart," Jaysura said.

She said the left ventricle of his heart was punctured with only one “deep” stab wound.

"Rather than getting help, he went to put the knife away — that's where we believe we have obstruction of justice," she said.

"Rather than getting help, he went to put the knife away — that's where we believe we have obstruction of justice."

— Maj. Tanzania Jaysura, lead trial prosecutor

The family of Barclay-Weberpal, of Janesville, Wis., listened via teleconference. His father told the Register after the hearing that he was glad the public could hear his son’s death was not the result of a fight.

The Associated Press contributed to this report.