Police say that the latest attacker, a woman, was hiding in a carport behind Derri Velarde's parking space in Mesa, Ariz. When Velarde, 41, arrived and got out of her car, the attacker threw concentrated acid in her face, and then fled.
"I don't know what could go through a person's head to do something like that," Velarde's son, David Dias, told a local CBS affiliate. "I mean if it was jealousy or trying to hurt someone's appearance like that, it's disgusting and wrong and there's a special place in hell for people like that."
Police are looking for a suspect described as a Hispanic woman between the ages of 30 and 40, according to Fox affiliate KSAZ-TV.
The attack was probably not an assault on a random victim.
"This type of crime is usually personal in nature; it's usually someone who's got an issue with the victim," Detective Mike Melendez told the local CBS affiliate.
On Monday, a Vancouver woman was attacked with an acid-like liquid as she stopped for coffee.
Bethany Storro, 28, had recently moved to Vancouver from Idaho to live with her parents. Storro's attacker -- described as an unknown black woman with slicked back hair in a pony-tail -- pounced when she was getting something out for the passenger side of her car.
Storro collapsed to the ground, screaming. Her face is badly swollen and she may need skin grafts to repair the damage.
"It's a very unusual incident, but we do occasionally have these odd kind of assaults,'' said Kim Kapp, spokeswoman for the Vancouver Police Department.
For now, both Storro and Velarde must suffer through their injuries and deal with the scars, mental and physical.
"At first she was happy to see us. Then you could see she broke down," Dias told the CBS affiliate about Velarde. "It's tough to see your mom like that."