Jeremy Davison/real name unknown was a serial rapist and murderer who along with his "sister" and accomplice, Michelle targeted and killed random people.
He was wanted by the FBI for five unsolved murders in Kansas City but at some point, they fled and later both arrived in Washington D.C, meeting hacker Victor Grotinski who gave them their new identities.
One night, Jeremy snuck into the Quantico Marine Base, intending to rape and presumbly kill Laura Rowens but she shot him in self-defense, prompting Jeremy to be taken to the Marine Hospital for treatment and also resulting in Special Agent Leroy Jethro Gibbs and his team being called in to investigate.
Eventually, it was revealed that Jeremy and Michelle were a serial-killing team and that Michelle was the one who had killed Grotinski.
The two left the hospital and attempted to get to safety, only to find Gibbs standing outside with Kate and Tony backing him with their guns drawn as well.
Michelle tried to get a gun to fight back but Kate stated that the first bullet from her gun would go through Michelle's right eye socket, forcing the two killers to surrender and be taken into NCIS custody, thus finally ending their vicious spree for good.
Jeremy's M.O. is not known but it's he presumed that the victims he often targeted were women. He would rape them before killing them, usually by strangulation or some other method.