Roberts: How could Avondale mother drown her own sons?

We begin the week with a home-grown horror story. Police say a young mother drowned her twin 2-year-old sons and attempted to drown a third  child.

It was just before noon on Sunday, in a suburban home filled with people.

We ask ourselves how and, of course, why.

How could Mireya Lopez, a 22-year-old old Avondale mother of three, allegedly hold the faces of her own children under the water in a bathtub until they stopped struggling?

How could it get so bad, that those closest to her didn’t see a problem? That Lopez was unreachable and thus her sons unsaveable?

Avondale Sgt. Brandon Busse told reporters on Sunday that Mireya Lopez confessed to intentionally drowning her twin toddlers and attempting to drown a third child -- a step brother.

Lopez, who had a history of mental illness, told investigators she drowned the boys because "nobody loved them and nobody loved her."

Neighbors were stunned, as neighbors… as everyone … must be.

"It's terrible," neighbor Shauna Siniscaochi told a reporter. "I'd never expect something like this to happen."

It goes against every instinct we have that such a thing could happen.

And yet it does happen.

On average, 450 children are killed every year by one of their parents, according to USA TODAY, which studied three decades of FBI homicide data last year.

Remember Andrea Yates? In 2001, she confessed to drowning her five children in the bathtub of her Houston home. She was found not guilty by reason of insanity.

Remember Susan Smith? In 1994, Smith, then 23, strapped her 3-year-old and 14-month old sons into their car seats and pushed the car into a South Carolina lake, drowning them. She is now serving life in prison.

She recently wrote a letter to a reporter saying she is “not the monster society thinks I am. I am far from it."

"Something went very wrong that night. I was not myself," Smith, now 43, wrote. "I was a good mother and I loved my boys ... There was no motive as it was not even a planned event. I was not in my right mind."

In fact, no mother could be. I just don’t believe it’s possible.