The article says:
Officers found 50 rounds of 44-caliber, 240 grain-jacketed Remington hollow point bullets, illegal in some states, including New Jersey, because they can pierce cops’ bullet-resistant armor, said Paul Loriquet, spokesman for the Essex County prosecutor’s office.
The problem is hollow point bullets are less able to penetrate body armor than the more common Full Metal Jacket (FMJ) bullets.
The fact that they probably were for .44 Magnum handgun is more telling. Almost any soft body armor comfortable enough for everyday wear is going to be penetrated by any full power load in that caliber.
But this is law enforcement in New Jersey where facts about guns are irrelevant to their jobs and when dealing with guns, the citizen acts at his peril.