My male does this as well - amazing how they still have that rat killing instinct!
I just let him play, although frequently I will ask him to "drop it" (once he drops the toy I give him a pat, and toss the toy back) so that the aggressiveness stays in check. He LOVES to play tug of war as well ... I read that that kind of play can make them more aggressive, although asking him to drop it periodically reminds him who is boss
and I haven't had any behavioral problems.
I think it's pretty normal, and wouldn't worry!