Bagaha Police district Superintendent of Police Anand Kumar Singh said Mr Gandhi had not reached the rally venue at Hazari Maidan when policemen caught the man as he arrived at the main entrance with the air gun.
The man has been identified as Tayyab Jaan, a resident of Jharmuhi village under Chautarwa Police Station in the district.
“He seems to be mentally unstable and claimed that he had brought the weapon for his own protection. We are investigating the entire episode in detail,” Mr Singh said.
He said a bag was also seized from the arrested man. It contained a few clothes and pellets used in air guns. He said that the police are inquiring the antecedent of the youth.
Rahul Gandhi addressed a rally organised to celebrate the 125th birth anniversary of Dalit icon BR Ambedkar.
Though RJD President Lalu Prasad and Chief Minister Nitish Kumar have given the programme a miss, Lalu Prasad Yadav’s son Tejaswi Yadav and JD(U) General Secretary KC Tyagi were representing the alliance partners.