HILLSBORO, Ore. -- One of the teens arrested after an assault on a light-rail platform near Hillsboro last month has had charges against him dropped after a Washington County grand jury voted against an indictment.

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Prosecutor Roger Hanlon says he can't elaborate on the reasons behind the grand jury's decision.

He also would not say whether the case will be resubmitted because charges were pending against another youth arrested in the case.

Background: Victim suffered fractured skull

The two teens are students at Westview High School.

They were alleged to be involved in a series of actions that began on the platform and ended with their car being used to ram two Forest Grove police patrol cars in an apparent attempt to elude police.

Police say the boy who still faces charges wielded a hammer and fractured the skull of a 12-year-old boy.

Sheriff's deputies say the attacks happened because the older boys believed the younger boys were members of a rival gang.