In 1913, he became editor of "The Bombay Chronicle", a daily founded by Pherozeshah Mehta. The paper adopted a trenchant anti-colonial voice and became a mouthpiece of the freedom movement under Horniman. Following the Jallianwala Bagh Massacre, Horniman managed to smuggle photographs of the incident and broke the story about the massacre and its aftermath in the Labour Party's mouthpiece the "Daily Herald". The exposé broke through the censorship on the matter and unleashed a wave of revulsion in the British public over the incidents and the Hunter Commission. One of his correspondents, Goverdhan Das, was imprisoned for three years. Horniman himself was arrested for his coverage of the massacre and criticism of the colonial government and deported to London, and the "Chronicle" closed down (temporarily).