Complex sentence: He deduces that Ms. Lewton is next, and rushes to her house to ensure her safety; but, thinking Alex is up to no good, Ms. Lewton calls the FBI agents, who take him in for questioning.
Split into simpler sentences: He deduces that Ms. Lewton is next, and rushes to her house to ensure her safety. Thinking Alex is up to no good, Ms. Lewton calls the FBI agents, who take him in for questioning.