An apparatus for penetrating bone and accessing bone marrow is provided. The apparatus may include a penetrator assembly and a powered drill. The penetrator assembly may include an inner penetrator having a stylet. The penetrator assembly may also include an outer penetrator having a hollow cannula and a luer lock attachment. The powered drill may include a housing enclosing a motor and a power supply and associated circuitry. The powered drill may also include a connector receptacle for receiving a penetrator assembly connector of the penetrator assembly. The powered drill may include a magnetic connection which releasably locks the penetrator assembly connector into place with the powered drill. The power supply may include a rechargeable battery within the housing for supplying power to the motor. A battery indicator may be provided to indicate a level of the battery.