The Xindi, an alliance of alien species, decided to send a large mobile particle beam superweapon to destroy Earth since they were being manipulated into believing that humans were evil and would destroy their future homeworld in the 26th century. Three of these weapons were built in total, with the final and biggest weapon’s goal being the complete destruction of Earth. The first one was merely a prototype, it bypassed Earth’s defenses and used a powerful particle beam to cut a 4,000-kilometer (2,485 miles) swath of destruction from Florida to Venezuela, killing 7 million people before self-destructing.

“There’s been an attack on Earth.”
“What do you mean, an… attack?”
“A probe. They don’t know where it came from. It fired a weapon that cut a swath 4000 kilometers long, from Florida to Venezuela. There may have been a million casualties.”

– Jonathan Archer and Charles Tucker III, 2153 (“The Expanse”)