A Middleboro police officer was seriously wounded during SWAT exercise when a training grenade detonated in his hand, police said. Bridgewater police and fire said they were called about 11 a.m. today by a member of the Southeastern Massachusetts Law Enforcement Council's SWAT team who requested an ambulance for an officer with a hand injury, police said. Medics found a Middleboro police officer with a "serious wound" to one of his hands, police said.