By the DC police/FBI best estimates, all activity ceased for Chandra as far as any identifiable trail about 1:00 p.m. when she logged off her computer. The time of day doesn't fit with this guy either. He planned his other attacks for after the park closed when there would be less chance of encountering anybody else.
We have no idea when in the day of May 1, (or even if it was the same day) she would have been killed. She may not have gone directly to park or she may have stayed several hours.