A swastika was discovered painted on a bathroom wall inside Tzalmon Prison in northern Israel, the Israel Prison Service announced Tuesday.

Video footage obtained by The Jerusalem Post shows the prisoner entering the bathroom, which is accessible from the prison yard, then exiting. He appears to stand close to the wall for several seconds before leaving. He is immediately met by a phalanx of prison officials, who take him away for questioning.

The only detail released publicly is that the prisoner holds foreign citizenship and has been disciplined for the incident.

Separately, Thiago Avila, a Brazilian flotilla activist who had been detained by Israel, returned to Sao Paulo Monday upon his release from detention by Israeli authorities. Avila alleged that he had been tortured and abused by Israeli authorities and that he witnessed far worse abuse of Arab prisoners.

Avila was detained for 10 days with Spanish-Palestinian activist Abu Keshek when Israel intercepted the Gaza Sumud Flotilla, which attempted to sail to Gaza to break the blockade. Israel intercepted the flotilla far from Gaza’s shore and released all the detainees in Crete except for Avila and Keshek, who they said had ties to a terror group.

Israel has denied the allegations of abuse.