 -- Police believe the mysterious double murder of two Maryland teenagers the night before their high school graduation was not a random crime.

Shadi Adi Najjar, 17, and Artem Ziberov, 18, were found shot dead the night of June 5 in a parked car on a residential street in Montgomery Village, about 23 miles north of Washington, D.C., Montgomery County police said. They were set to graduate from Northwest High School in Germantown the next day.

One teen was shot 10 times, while the other was shot four times, Capt. Darren Francke, director of Major Crimes for the Montgomery County Police Department, said today. More than 30 casings from multiple guns were found at the scene, police said.

Police still have no suspects are asking for the public's help in solving the case, Francke said today. He said police believe there was more than one shooter and believe the perpetrators and at least one of the victims knew each other.

Francke said it’s likely that peers from the victims' high school know about the crime, and he appealed for any student with information to share it.

The families of both teenagers are grief stricken, but have been very cooperative, Francke said.

He said Najjar's family is working to increase the reward money from the current $10,000 sum to $20,000, and he said people who might have information need to come forward and speak with police. Before Najjar's funeral, his father begged for information to find the teens' killers, reported ABC affiliate WJLA-TV.

At what would have been their graduation ceremony, a moment of silence was held for the slain teenagers. The principal said he planned to deliver the teenagers' diplomas to their parents.