One man was enforcing the law, the other was going out of his way to obey it. Both paid for these acts of civic virtue with their lives, gunned down by a paroled offender.

The men lost were Officer Arthur Lopez, 29, a Nassau County policeman from Babylon Village with a big heart and a cherubic face, and Raymond Facey, 58, known on his block in East New York for an over-the-top neighborliness and generosity.

Their alleged killer is Darrell Fuller, 33, who had served time for attempted murder and was on parole for a different crime at the time officials say his violent path intersected lethally with the lives of Lopez and Facey.

Lopez died as he and his partner in the elite Emergency Services Unit pursued a suspect on the Cross Island Parkway. When they caught up to the car, police say that Fuller got out and shot Lopez in the chest. Minutes later, Fuller allegedly found Facey on the side of the parkway, where he had pulled off to take a call from his daughter -- so as not to disobey the cellphone law -- and then pulled Facey from the car and shot him.

Both deaths have left their families deep in grief, wondering about the cosmic injustice of it all. For Lopez, the stricken family includes his brother and sister officers, shocked and tearful. His death came only one day after the funeral of Officer Joseph Olivieri, struck and killed on the Long Island Expressway as he helped a driver who turned out to have been drunk.

It was the first time that anyone could remember a Nassau officer being killed the day after another officer's burial. On the last full day of his life, Lopez attended that funeral.

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There will be time later to seek answers: Why was Fuller on the street? Did the parole system work as it should? Where did he get the pistol he used to take two lives? Should police enforce more rigidly the policy on wearing bulletproof vests?

For now, it's time to provide these families comfort in their grief, to begin the long healing process. Focusing too much on these questions right now won't help shaken relatives cope with this tragedy. But soon enough, they -- and we -- will need clear and unequivocal answers. And the county and the state must find them.