it. the last back to school speech met with criticism of conservatives. he received praise from both parties for delivering a positive message on education. but we have seen that natural gas explosion and what it did to san bruno, california. let rewind. take a look that the security video. on the left you see the smoke rising and then boom. explosion and fire ball 6:07 p.m. pacific time. this video is from inside a market. you can t see the blast but the shoppers sure do. some run out to see what happened. others don t know whether to stay or go. it s a chaotic moment there. on that thursday evening. four people still missing in san bruno, by the way. at least four people were killed and pg&e said they ll help pay off that emergency.