Li said he was buying lottery tickets when a gunman entered and tried to break down the glassed-in secure area behind the counter.
Li called again and got a different operator but by the time police responded, the store's owner - 51-year-old Zia Arfeen Seddiqui - was dead.
In another incident on March 13, a security guard called to report two motorists driving recklessly as they raced each other at high speed on 1-45 South.
Williams was the operator, according to police - and she allegedly terminated the call before the guard could give his full name.
Police said they questioned Williams about these incidents in June.
She told them she "often hangs up on calls that have not been connected because she did not want to talk to anyone at that time," according to Click2Houston.
Williams is set to appear in court next week.