BAKERSFIELD, Calif. -- The five teenagers accused of beating an 81-year-old man to death face a combined 40 felony counts.

It's a crime that District Attorney Ed Jagels calls one of the worst he's ever seen. “This is an unbelievably vicious crime,” Jagels said. “One of the worst that I've encountered.”

During Wednesday's court proceedings, four of them pleaded not guilty to charges including murder, elder abuse, robbery and participation in a street gang. One of the teens has a later court date.

Police said the five boys beat Ezequiel Perez to death in an alley south of Niles Street Saturday morning while he was collecting cans. Police said the teens came back and beat the man a second time after initially beating him. They also said several of the man’s belongings were found at the home of one of the teens. Police confirmed that the teens also stole the man's aluminum cans after beating him.

Related Blog: Are Gang Kids Out Of Control In Bakersfield?

An eyewitness to the beating said the teens are no strangers to violence in their east Bakersfield neighborhood.

One witness who has come forward said at least one of the teens “shot our house a couple times with a BB gun.” The witness said he saw the group of five boys beat Ezequiel Perez to death and that he's sickened by the attackers' behavior and should have helped. The witness would not appear on camera.

According to officials, Demetris King, 15; Nathaniel Johnson, 14; and Christopher Jones, 14, can be tried as adults. They face life in prison if convicted.

Jones' mother says he was an innocent bystander. “He don't even know them boys,” said Marilyn Jones.

The other two teens, William Wandick, 13, and Robert Smith, 13, must be tried as minors under state law.

If convicted, each could be in custody until they turn 25.