He was arrested after participating in a religious ceremony along with families of political prisoners and several reformists.

According to the witnesses, plainclothes agnets were all over the place even though the location was quite and there were no protests.

One of the plainclotehs agnets approched Karami and asked him to accompany him. He then took him to a police vehicle
He was previously arrested in February for the charges of conspiracy aginats national security by persuading people to jon the February 14th protests and anti-regime propaganda. He was sentenced to one year in prison.
Persian Article: http://www.rahana.org/archives/43662