The chief executive of a major U.S. steel manufacturer has died unexpectedly just three weeks after taking over the company’s top leadership role. Brian Malloy, 59, died suddenly on Friday after being named CEO of Carpenter Technology Corp., a 137-year-old Pennsylvania-based manufacturer that produces specialty stainless-steel alloys for the medical, aerospace, and defense industries and is valued at approximately $3 billion. Following Malloy’s death, the company announced that Thene will return to lead Carpenter Technology while the board determines its next steps. Despite his unexpected death, the company said the earnings presentation will proceed as scheduled. The sudden loss also rattled investors; shares of Carpenter Technology fell about 4 percent Monday to roughly $580 after news of Malloy’s death became public, according to the Philadelphia Inquirer.