Bill Cooke of NASA'S Meteoroid Environmental Office said it appeared to be a "a single meteor event." Derrick Pitts, chief astronomer at Philadelphia's Franklin Institute, told AP the flash was likely one meteor or a "space rock." Pitts also added it is difficult to be "100 percent certain of what it was," but that the given descriptions seemed consistent with a meteor.
Above, footage captured by security cameras at Hopkins Automotive in Salisbury, Md. The footage has not been confirmed, but could plausibly depict the meteor due to factors such as timing, location and relative positioning of the company on its block.
The object was described as bright green in color and visible for about 40 seconds. It was also described in multiple accounts as "sparking" or "flashing."
So far, there are no conclusively confirmed photos of the event. Several photos have circulated Twitter and Facebook, purporting to depict tonight's event, but at least two of the most widely shared of these depict earlier events (see here and here).
In addition, reports of an impact in Delaware have circulated. However, these may also be false.