It is just absolutely inaccurate to depict an NCIS team doing a high risk arrest of the CEO of a private security company alone and without backup. The training grounds of this company are filled with heavily armed, experienced soldiers and special forces operators, there is no way an NCIS team would execute an arrest such as this without an NCIS REACT team backing them up.
Boone asks if the high levels of aluminum in the victim's tissue was from the bullets he was shot with, and Kai points out that bullets are almost always made from copper and lead. Boone has been in law enforcement his entire career, the training he had to become a police officer, and then a federal agent, and his job would make him familiar with the composition of bullets, not the kind of mistake he would make. Over 90% of bullets are indeed made from a lead core and a copper jacket, and certain types of armor piercing bullets are made with a steel core and either a tungsten or depleted uranium jacket. There are a few rare types of hunting ammo whose bullets have an aluminum tip, but these kind are rare and would not come close to leaving enough aluminum in a body to show up on a toxicology screen.