RICHMOND, Va. — Seven people were shot, two fatally, when gunfire rang out Tuesday outside a downtown theater where a high school graduation ceremony had just ended, causing hundreds of attendees to flee in panic, weep and clutch their children, authorities and witnesses said. A 19-year-old suspect tried to escape on foot but was arrested and will be charged with two counts of second-degree murder, Interim Richmond Police Chief Rick Edwards said during a nighttime news conference at which he confirmed the two fatalities. Five others were wounded by the gunfire outside the state capital’s city-owned Altria Theater, which is across the street from a large, grassy park and in the middle of the Virginia Commonwealth University campus.