(LONDON) The man arrested on Tuesday night for throwing what appears to be shotgun shells in the grounds of Buckingham Palace has been detained, London police said on Thursday.

Apprehended “under the Mental Health Act”, which allows authorities to arrest and treat someone with mental health issues without their consent, the 59-year-old was “taken to hospital”, police said in a statement.

“He will remain on bail while receiving medical treatment,” she added.

The man was arrested around 7 p.m. Tuesday (2 p.m. EST) on suspicion of being armed with a knife and after approaching the palace gates and throwing what may be rifle cartridges.

Security forces also blew up a bag belonging to the suspect as a precaution, following the arrest, which came days before Saturday’s coronation of King Charles III, which is to be attended by sovereigns and other leaders around the world.

According to British media, neither Charles III, 74, nor his wife Camilla, 75, were at the palace at the time. The king’s services did not comment.

The thoroughfare leading to Buckingham Palace has been closed to traffic ahead of the coronation, the first to take place in the UK for 70 years.

Thousands of soldiers will take part in a procession from Buckingham Palace to Westminster Abbey and huge crowds are expected.

The security operation to protect this route is one of the largest in recent years in the UK. It will rely on rooftop snipers and undercover agents, as well as airport-style detectors, sniffer dogs and a no-fly zone over central London.