LONDON (AP) — UK police say the final person being questioned in the March 22 terror attack has been released with no further action.

The 30-year-old man arrested in Birmingham on suspicion of preparation of terrorist acts was released Saturday. No further action is planned against him or 11 others arrested in the probe.

Authorities have said they believed Khalid Masood was acting alone when he drove down Westminster Bridge, mowing down pedestrians and killing three. Masood then fatally stabbed a policeman in a courtyard on the grounds of Parliament.

Police believe British-born Masood’s 82-second rampage was inspired by extremist ideology, though authorities say there is no evidence he had direct links to the Islamic State group or al-Qaida.