Well, there is something suspicious about this since there are multiple accounts across media that there were multiple shooters.
But all we are hearing about now is one lone gunmen.
There are apparently at least one, possibly 2 to 3 accounts of multiple shooters documented within a few hours of the incident. A good investigator knows that the best time to take witness accounts is as close to the time of the act as possible. Information tends to be more reliable. The sooner the better.