This article is dated July 20. The day of the shooting.
The mother made her statement a few days later.
They called her the morning of the incident.
The mother made her statement at 0545hrs the day of the incident.
It is easy to understand that it took her a couple of days of dealing with the fact her son did such a vile thing before she could pay attention to the media. It was then she rightfully issued the statement calling ABC a liar.