Opening statements were heard Thursday in the trial of a New Jersey state park police officer who is accused of killing a Native American man from Monroe.

The defense claims that Officer Chad Walder was provoked by 45-year-old Emil Mann and was forced to shoot him to preserve his own life. The prosecution, however, insists Walder deliberately pulled the trigger on the victim.

The incident happened April 1, 2006, when Mann attended a cookout at Ringwood State Park in Mahwah, N.J. with family and friends. Assistant Bergen County Prosecutor James Santulli says Mann was caught riding an ATV illegally and had an altercation with Walder that ended with the officer shooting Mann twice in the thigh and chest. Santulli told jurors Walder used bad judgment and panicked.

"He was standing there with his hands up in the air," Santulli says. "He was shot and killed when he didn't have to be."

Defense Attorney Bob Galantucci presented a different version of events. He said Walder heard screaming and saw his lieutenant being attacked by Otis Mann, the victim's cousin. As Walder rushed to help his colleague, Galantucci said, Mann came out from behind a tree and jumped on Walder.

"He was finally able to take his gun out and he said, 'stop,'" Galantucci told the jury. "Mann said, 'shoot me, f---ing shoot me,' and then...he lunged for the gun."

Testimony will resume Tuesday. The trial is expected to last approximately two weeks. If Walder is convicted of manslaughter, he faces 10 years behind bars.