SANAA, Yemen — A crowd apparently spooked by gunfire and an electrical explosion stampeded at an event to distribute financial aid during the Muslim holy month of Ramadan in Yemen’s capital late Wednesday, killing at least 78 people and injuring at least 73 others, according to witnesses and Houthi rebel officials. The tragedy was Yemen’s deadliest in years that was not related to the country’s long-running war, and came ahead of the Muslim holiday of Eid al-Fitr, which marks the end of Ramadan later this week. Armed Houthis fired into the air in an attempt at crowd control, apparently striking an electrical wire and causing it to explode, according to two witnesses, Abdel-Rahman Ahmed and Yahia Mohsen.