In the 1930s, Charles Reber, a US Army veteran of the Spanish-American War and an ex-Major with the Oklahoma National Guard, was a pioneer ballistics and fingerprint expert with the Oklahoma State Bureau of Investigation & Identification, who consulted on numerous cases.
This alone would make him an interesting example for an Investigator of the Mythos. During the hunt for Charles “Pretty Boy” Floyd, he was also painted as a template for an Armed Investigator in newspaper articles like “One-Man Army Rigs Auto for Sudden Battle” in The Fresno Bee (08-JUN-1934):
Though he looks like a staid schoolteacher [!], is quite and unassuming, Reber is as expert with a gun as with his ballistics apparatus … Inside his sedan he has rigged out a rolling arsenal. By reaching up with his left hand he can pull a sawed-off shotgun, loaded with buckshot, from a rack in the car. With his right hand he can claw down a Browning automatic rifle. Reaching forward he can pull a Thompson sub-machine gun from a rack on the dash of the car, where it is flanked by holders containing clips [sic] of ammunition. In the seat with him he can reach a Colt .45 automatic or a long-range German Luger automatic of smaller caliber, but deadly accuracy. On the floor, in a case, he can reach hand grenades, [tear] gas bombs and extra clips [sic] of ammunition ‒ shotgun shells, high power rifle cartridges and pistol ammunition, all carefully arranged to be “handy.” In the back seat, for long range work, he has an old Krag-Jorgensen [sic] army rifle, made famous in the Spanish-American war for its deadliness. Its sights are carefully adjusted, with wind gauge, elevation, and important other arrangements.
In short, he had a double-barrelled shotgun with sawn-off barrels, an M1918 BAR (GURPS High-Tech: Pulp Guns 2, p. 11; Investigator Weapons 1: The 1920s and 1930s, pp. 63-64), a Thompson submachine gun (GURPS High-Tech: Pulp Guns 1, pp. 28-30; Investigator Weapons 1, pp. 87-89) ‒ either a personally-owned weapon or one of the three Auto-Ordnance Model 1928AC submachine guns (No. 6670, No. 6947, or No. 8800) acquired in 1933 by the Oklahoma State Bureau of Investigation & Identification ‒, a Colt Government-type semiautomatic pistol ((High-Tech: Pulp Guns 1, pp. 17-18; Investigator Weapons 1, pp. 37-38), a Luger l.P.08 semiautomatic pistol (High-Tech: Pulp Guns 1, p. 16; Investigator Weapons 1, pp. 45-46), a Krag-Jørgensen M1898 bolt-action rifle (High-Tech: Adventure Guns, p. 34), and several MK II fragmentation hand grenades (High-Tech: Pulp Guns 2, p. 31; Investigator Weapons 1, p. 98) and tear gas hand grenades (High-Tech: Pulp Guns 2, pp. 30-31; Investigator Weapons 1, p. 98) in his car.
Although he sounds like a well-rounded and interesting chap, Reber was less likeable than it would appear. He was a prominent member of the Ku Klux Klan who in 1922 led a mob of hundreds who flogged two African-American taxi drivers in Shawnee, Oklahoma.
His abilities as a ballistics expert were also suspect; in at least one case in 1933, he misidentified .45 ACP cases as having been fired from two Thompson submachine guns and a Colt Government-type semiautomatic pistol when they actually were fired from a single S&W M1917 revolver.
Finally, his claims that he had shot and wounded Floyd with a tracer bullet from a BAR on 07-JUN-1932 in Stonewall, Oklahoma, have never been proven.
Other Armed Investigators might nevertheless be interested to hear that resourceful Jazz Age law enforcement officers (Occupation Police Detective) would be able to acquire not only Thompson submachine guns but also BARs and grenades if required.