Internal defects are an inherent quality of powder bed fusion additive manufacturing (PBFAM). The types of defects and the process parameters that cause them to form within PBFAM parts are heavily studied in the additive manufacturing community as a means to maximize part density. However, the mechanisms that cause individual defects to form mid-process are largely not understood, specifically when they form under ideal process parameters. In the outlined experiment, two in situ high-speed imaging systems monitoring melt pool and plasma plume behavior are used to investigate and characterize the defects generated during the process of a commercial 3D Systems ProX-320 PBFAM machine. During the fabrication of a cylindrical test coupon, machine parameters and process conditions linked to defect formation are manipulated by the use of a novel powder delivery system to elicit more naturally forming defects associated with part failure. Synchronization between the PBFAM machine subsystems (i.e. laser and scanner) and X-ray computed tomography of the processed coupon reveals the success of each parameter and process manipulation in generating internal defects at precise locations, while high-speed videos of the corresponding layers recorded at rates up to 25,000 frames per second reveal the process mechanisms and laser-material interactions that lead to or are caused by said defects.