Throw his phone one way, and run the other.

You don't need his phone any more, but you're hoping he still cares about it more than he cares about hurting you. You lob the phone to his left and simultaneously run to his right, heading for the door on the other side of the room. Luckily your plan works as he ignores you and tries to catch the phone. You don't dare look back, but the loud cracking sound followed by a bellowing "FUCK!" tells you he didn't manage it.

"You're fucking dead!" He shouts, but by the time he finishes yelling you're already out the bathroom and long gone.