Behbahani supported the moderate group and became an influential person when differences of opinion arose between the two groups, causing the ultra progressive deputies led by Sayyed Hasan Taqizadeh to dislike him. On the night of Friday 15 July 1910, four gunmen associated with the Social Democrats attacked him at his home and killed him. Seyyed Hassan Taghizadeh was suspected to be responsible, and he subsequently fled the country.[1][7] Haydar Khan Amo-oghli had organized the assassination.[8] Behbahani's body was transferred to Najaf and buried in the courtyard of the Imam Ali Mosque.[9]