ZURICH—An Austrian of Afghan descent whose genetic material was allegedly found on the weapon that a jihadist used to kill four people in Vienna last month has been arrested, prosecutors said on Sunday. Authorities will seek court approval to put the 26-year-old into investigative custody, a spokeswoman for Vienna prosecutors said, confirming a report in the Krone newspaper. “Traces of DNA from this person were found on the weapon,” she said. Another suspect was also arrested, she said, without giving details. Police shot dead the 20-year-old gunman, whom Austrian authorities have described as a  radical Islamic terrorist, during his rampage in the center of the Austrian capital in early November. Austria had already arrested 15 people in connection with the attack. Authorities in Germany and Switzerland are also investigating people they suspect had ties to the shooter.