Getty Images A trader on the New York Stock Exchange on Oct. 19, 1987 — Black Monday.When the stock market crashed on Oct. 19, 1987, investors panicked. It was an unfamiliar event — the previous decline of a similar magnitude occurred 58 years earlier, in 1929. Now, 30 years after Black Monday in 1987, there are professional investors still at work who lived through that fateful day. In interviews, three of them talked about their experiences, offered insights into warning signs and gave advice on how to handle major downturns. They are: • Lewis Altfest, president of Altfest Personal Wealth Management, which manages about $1.3 billion for private clients. Altfest founded the firm in 1983 after working as a general partner and director of research at Lord, Abbett & Co. • Brian McMahon, chief investment officer of Thornburg Investment Management, co-manages the $2.5 billion Thornburg Global Opportunities FundTHOAX, +0.54% and the $16.1 billion Thornburg Investment Income Builder Fund TIBAX, +0.09% In October 1987, McMahon was managing Thornburg’s laddered maturity bond portfolios. • Lawrence Haverty, associate portfolio manager of the $231 million Gabelli Multi-Media Trust GGT, -0.11% In October 1987, Haverty co-managed the Putnam Growth Fund and the Putnam Convertible Fund, which had combined assets of about $2 billion.via