news the suspect posted disturbing messages online before the shooting, which is just one of many over the holiday. authorities in shreveport are searching for the suspect wanted for killing four people at a birthday block party. 18 people killed, more than 100 wounded in mass shootings over the last four days. trevor ault is in philadelphia. record-breaking heat and travel. more than 50 million americans are now making the return trip home after the long holiday weekend. the tsa screening an all-time high of 2.8 million in one day. and tonight, a new round of severe storms from denver to chicago. heat alerts from oregon to florida into the northeast. and the new record for the hottest day on earth. tensions rise in the gulf of oman. the u.s. navy releases video showing an iranian naval ship, accusing iran of trying to seize two foreign oil tankers in international waters, firing at one of them. a u.s. navy destroyer racing to protect the ships. marcus moore standing by.