<P> Willoughby brings Mildred in for questioning after she drills a hole in her dentist's thumb when he threatens her . During the interview, Willoughby coughs up blood . He leaves the hospital against medical advice and spends an idyllic day with his wife Anne and their two daughters, then commits suicide due to his illness . He leaves suicide notes for several people, including Mildred, in which he explains that she was not a factor in his suicide and that he secretly paid to keep the billboards up for another month, amused at the trouble this will bring her and hope that they will keep attention on the murder . Dixon reacts to the news of Willoughby's death by assaulting Welby and throwing him out of a window . This is witnessed by Willoughby's replacement, Abercrombie, who fires Dixon . In the meanwhile, Mildred is threatened by a crop - haired stranger in her store . </P> <P> The billboards are destroyed by arson . Mildred retaliates by tossing Molotov cocktails at the police station, which she believes is unoccupied for the night . However, Dixon is there to read Willoughby's letter to him, which advises him to let go of hate and learn to love, as the only way to realize his wish to become a detective . Dixon escapes with Angela's case file but suffers severe burns . Mildred's acquaintance James witnesses the incident and provides Mildred with an alibi, claiming they were on a date . Dixon is treated for his burns, and he is temporarily confined in the same hospital room as Welby, to whom he apologizes . </P> <P> Discharged from the hospital, Dixon overhears the man who threatened Mildred bragging in a bar of an incident similar to Angela's murder . He notes the Idaho license plate number of the man's vehicle, then provokes a fight by scratching the man's face . At home later, he removes a sample of the man's DNA from under his fingernails . Meanwhile, Mildred goes on a date with James to thank him for the alibi . Charlie enters with his 19 - year - old girlfriend Penelope and admits to burning the billboards while intoxicated . After accidentally causing James to leave, Mildred tells Charlie to treat Penelope well and leaves . </P> <P> Though commending him, Abercrombie informs Dixon that the DNA sample does not match DNA found on Angela's body, and that the man was overseas on military duty at the time of the murder . Dixon concludes that the man must be guilty of some other rape, and joins Mildred on a trip to Idaho in order to kill him . On the way, Mildred confesses to Dixon that she set the police station on fire . He indicates that he knew already . They express reservations about their mission but agree to decide what to do along the way . </P>

Who burned down the billboards in three billboards