A spokeswoman for Cinemark had no immediate comment Friday on the letter or on Tom Sullivan's column.
Sullivan's column did not criticize the families who are refusing to attend.
"I will never tell anyone what is the right way or wrong way to grieve the loss of a loved one," he wrote. He offered to support anyone else who does attend.
"The seat next to me will be saved for Alex, but I'll have an extra hand if you need something to hold on to," he wrote.
Sullivan also expressed his gratitude for the outpouring of support his family received from Aurora and elsewhere.
A victim representative for the Sullivan family didn't immediately respond to an email Friday.
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