What's the surname of the man who dies of a heart attack?  Answer the above question based on the context below:  On the planet Krypton, Jor-El of the Kryptonian high council discovers the planet will soon be destroyed when its red supergiant sun goes supernova. Despite his insistence, he fails to convince the other council members. To save his infant son, Kal-El, Jor-El launches him in a spaceship to Earth, a planet with a suitable atmosphere where his dense molecular structure will give him superhuman strength and other powers. Shortly after the launch, Krypton's sun explodes, destroying the planet. The ship crash-lands on Earth near Smallville, Kansas. Kal-El, who is now three years old, is found by Jonathan and Martha Kent, who are astonished when he lifts their truck. They take him back to their farm and raise him as their own, naming him Clark after Martha's maiden name. At 18, soon after Jonathan's death from a heart attack, Clark hears a psychic "call" and discovers a glowing green crystal in the remains of his spacecraft. It compels him to travel to the Arctic where it builds the Fortress of Solitude, resembling the architecture of Krypton. Inside, a hologram of Jor-El explains Clark's true origins, and after 12 further years of educating him on his powers and his reason for being sent to Earth, he leaves the Fortress wearing a blue and red suit with a red cape and the House of El family crest emblazoned on his chest and becomes a reporter at the Daily Planet in Metropolis. He meets and develops a romantic attraction to coworker Lois Lane.
A:
Kent