I know it always sucks when people lose their lives but, as arrogant and as devilish at it might sound, I am actually more interested in how the whole incident happened in the first place, the context for the explosion, in this case.
Gas seems to be the most logical explanation, a gas leak that went unnoticed until they lit a flame. 10:23AM on a Saturday. Allows time to sleep in (no need to get up earlier for work since it's a weekend, a lot of jobs allow a weekend off). It's around the perfect time to have had some extra sleep and then gone to have some breakfast, possibly leading to gas and flame being used by an oven. It'd also be interesting to know if the household had any propane tanks stored nearby.
Gas always has a smell to it, so more often than not you can notice a leak by smell. (I'm sure there's a fart joke in there somewhere). But seriously, they are fairly easy to avoid, providing that you catch on to the leak early to turn off the gas supply. If it all happens at night while sleeping, then it's more difficult to catch it early, although I imagine they would've easily smelled large amounts of gas in the house once they woke up.
But then, we are assuming it is an accident. It might well be that one of the family might have been in poor mental health and set the event to occur. Or if a raccoon or a rat has bitten through a gas pipe during the night. Anything is a possibility until we get more concrete evidence.
Yes, it is always best to keep active alarms in rooms that have appliances which use gas. Check up on the alarms every 6 months/year to ensure they are still working and functioning. Replace batteries in battery operated ones etc etc.
Again, assuming it is a gas cause. The explosion seemed large enough to be gas. However it could have been an electrical fault/spark that set off the explosion, from faulty electronics or wiring that has gotten old or eroded over the years for whatever reason.
An investigation should occur to surmount the situation.