Wondering if there is any news on SN4, appeared to be a problem with ground equipment?
Discussion and photo analysis on the NASA forums seems to indicate the Ground Service Equipment (GSE) rapid disconnect fuelling/defuelling connectors failed and allowed methane and LOX to mix below SN4 which then ignited. Consensus is that there was nothing wrong with SN4 itself before the explosion.
Pad itself will need repair, and debris landed in the tank farm. But Spacex have redundancy as they have prototypes being built on both coasts.