Story highlights Two killed the night before graduation, police say

Motive for the shootings of Artem Ziberov, 18, and Shadi Najjar, 17, is unclear, police say

(CNN) Two Maryland high school seniors were found shot dead in a car the night before their graduation.

Who killed them or why remains a mystery, according to police.

Artem Ziberov, 18, and Shadi Najjar, 17, were found late Monday in Shadi's car, which was running when officers responded to a 911 call of shots fired, according to Montgomery County Police.

More than a dozen shots can be heard on a neighbor's surveillance footage obtained by CNN affiliate WJLA.

"Why would somebody kill my boy, my beautiful boy ... days before graduation," Adi Najjar, Shadi's father, told reporters.

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