Sources on Twitter have posted photos and videos of the situation and have said that the gunfire is part of a coup attempt. The king has reportedly been evacuated.
BREAKING: A number of journalists in Riyadh are reporting heavy fire outside palace compound. Crown Prince Mohammad bin Salman, per these sources, has been evacuated to a bunker inside a military base in the city. Information coming in is still fluid, remains unconfirmed.
— Daniel Medina (@dmedin11) April 21, 2018
— The Intel Crab (@IntelCrab) April 21, 2018
Source: The Jerusalem Post