Of course it could. It could also be a black man or black woman. The odds are against this,though. The vast majority of serial killers are white males.
BTW,WHY does everybody keep assuming this is a rifle being shot? Anybody ever heard of the Thompson Contenders,or the Remington bolt-action pistols? I used to have a .223 Contender with a 2x Bushnell pistol scope,and it was no trouble at all to hit bricks at 100 yards.
The TC could be used, but if you assume this to be the work of a terrorist team (IMO), it would make more sense for it to be a AR-15. Such a team would want the firepower if they got into a confrontation with LEO. Much the same way that sniper teams have a shooter on a bolt gun and a spotter with a M16 or M14 for backup if they get closed in on.