The oil market and the U.S. stock futures were calm early on Monday morning after the U.S. was rattled by the assassination attempt on former president Donald Trump during a rally in Pennsylvania this weekend. Investigation showed that the shooter acted alone – a development that prevented a pronounced negative effect on U.S. markets. S&P 500 and NASDAQ futures were rising in pre-market trading on Monday, pointing to higher opening, as markets do not appear rattled by the shooting at Trump’s rally. As of 7:50 EDT…