Complex sentence: Vanek fights Becket in hand-to-hand combat as he enters the labs beneath Wade Elementary, where Becket kills him by shooting him in the head with Vanek's own shotgun.
Split into simpler sentences: Vanek fights Becket in hand-to-hand combat as he enters the labs beneath Wade Elementary. Ultimately, Becket manages to kill him by shooting him in the head with Vanek's own shotgun.