The murder of an active duty member of the U.S. Army would not be investigated by the local police, especially if the murder was committed by another member of the Army while being on a Army base. Serious crimes committed on a U.S. Army base or against its personnel fall under the jurisdiction of Army C.I.D. (United States Army Criminal Investigative Division) which is a federal law enforcement agency staffed by members of the U.S. Army and is tasked with "investigating felony crimes and serious violations of military law & the United States Code (U.S.C.) within the United States Army."
Fayetteville is not a small little town with a quaint little sheriff's department off some back road in rural NC. Along with a metro population over 500,000 and Fort Bragg, the largest military installation of the United States Army in the world (by population) with more than 50,000 active duty personnel, it's the home of the Army's XVIII Airborne Corps and is the headquarters of the United States Army Special Operations Command, which oversees the U.S. Army 1st Special Forces Command (Airborne) (Provisional) and 75th Ranger Regiment.[3] It is also home to the U.S. Army Forces Command, U.S. Army Reserve Command, and Womack Army Medical Center. Fort Bragg maintains two airfields: Pope Field, where the United States Air Force stations global airlift and special operations assets as well as the Air Force Combat Control School, and Simmons Army Airfield, where Army aviation units support the needs of airborne and special operations forces on post.
Most of the scenes don't resemble Fayetteville in any way, shape or form.
Dean tries to electrocute Cole with two car batteries. Cole reacts as if he was hit with line voltage AC, which, without an inverter (which they don't have, judging by the alligator cables Dean uses - they go directly to the battery) could not be produced by two car batteries. All batteries generate DC, which is far less dangerous and would not hurt anywhere near as much as AC. 100VDC is far less dangerous than 100VAC (even 100Vpp). DC can get dangerous but only at extremely high voltages (the average Taser hits with 50,000V), but the highest voltage that one can produce with two fully charged car batteries is around 28V. Human skin has a naturally high electrical impedance, typically around 500 ohms, as such it takes a minimum of 50V to carry enough current through the layers of skin and cause enough damage to inflict serious pain. Anything less than 50V just feels like a tingle.