From the Document: "Based on the 2016 Survey of Prison Inmates (SPI), about 1 in 5 (21%) of all state and federal prisoners reported that they had possessed or carried a firearm when they committed the offense for which they were serving time in prison. More than 1 in 8 (13%) of all prisoners had used a firearm by showing, pointing, or discharging it during the offense for which they were imprisoned. Fewer than 1 in 50 (less than 2%) of all prisoners had obtained a firearm from a retail source and possessed, carried, or used it during the offense for which they were imprisoned. An estimated 287,400 prisoners had possessed a firearm during their offense. Among these, more than half (56%) had either stolen it (6%), found it at the scene of the crime (7%), or obtained it of the street or from the underground market (43%). Most of the remainder (25%) had obtained it from a family member or friend, or as a gift. Seven percent had purchased it under their own name from a licensed firearm dealer."
NCJ 251776; National Criminal Justice 251776
Bureau of Justice Statistics: https://www.bjs.gov/