Jayasundara was on assignment for Wijeya Publications, a sponsor of the event and publisher of several English- and Sinhala-language newspapers and magazines.
He was standing in the area between the stage and the VIP enclosure when the grenade exploded, according to news reports.
The Sri Lankan government vowed a full investigation into the case, which it has called "a mindless attack by lawless elements." No group took responsibility for the attack. A hotel employee was also killed, and many others were injured, according to news reports.
The show featured Bollywood stars such as Shahrukh Khan, drawing thousands of spectators and setting off protests in Colombo. Hours before the grenade exploded, police clashed with demonstrators who were angry that the musical event coincided with the first anniversary of the death of Buddhist cleric and Sinhala Buddhist nationalist Ven. Gangodawila Soma Thera.