U.S. stocks had a lazy start to the week after the three-day Easter weekend, securing a mixed close in an undecided session. Trading was also skittish after news broke late in the day of gunfire at the U.S. Capitol visitor center, prompting a lockdown of the building and the White House. Starwood Hotels (HOT) climbed after Chinese company Anbang Insurance Group raised its buyout offer. The latest proposal trumps a previously-accepted merger offer from Marriott International (MAR) - Get Report . Qlik Technologies (QLIK) jumped on reports it is exploring strategic alternatives, including a possible sale. Avon (AVP) - Get Report confirmed it has decided upon an agreement with a group of investors led by Barington Capital Group to appoint an independent director to its board.