The pistol used by a disgruntled designer to kill a former co-worker outside the Empire State Building on Friday is among the more lethal handguns on the American firearms market.

The police said the shooter, Jeffrey T. Johnson, 58, used a .45-caliber semiautomatic pistol that held seven rounds. Law enforcement officials said Mr. Johnson bought the pistol in Sarasota, Fla., in 1991. Police Commissioner Raymond W. Kelly later identified the gun’s manufacturer as Star, a Spanish company that is no longer in business. Mr. Johnson did not have a concealed-carry or residential permit in New York, so his possession of the weapon was illegal in New York City, according to city officials.

The .45-caliber semiautomatic was the standard sidearm for the American armed forces for much of the 20th century. The semiautomatic feature means that the gun reloads automatically after the trigger is pulled and a round is fired; it fires larger rounds than most handguns, making it difficult to handle, but powerful.

“If you don’t know what you’re doing, you’re probably not going to be able to hit the broad side of a barn with it,” said Joseph F. King, a former United States Customs Service special agent. But, he added, “If you can put a round in center mass of the body, or the head, he’s probably not going to make it.” The firearm, powerful as it may be, is not the subject of much of the debate about gun control.