There was a person there, and they were using hydraulic equipment to detension a rod that went through one of the concrete diagonals. One of the workers perished, and it might have been him. The crane wasn’t attached to the span, but was holding test equipment and may have lifted the worker to his post.
If you have time to skim through the link above, there are now three pages of smart engineers discussing this. Their consensus seems to be that the concrete truss design was not sufficiently robust to begin with, and that the tension adjustment was likely the precipitating factor for the collapse, but not the underlying source of the deficiency. There are a number of comments about the span being too long and the elements too thin, in addition to a recurring theme that concrete trusses are not a good choice for such service.
A new factor of interest is that the design of the bridge was modified in mid-design because the State required that the support be moved to allow for future road lane additions. This added about 10 feet or more to the span, and apparently required a re-do of all the design and calculations.
There also seems to be a consensus that traffic ought to have been shut down while the adjustments to the span were underway. Interestingly, there is a general respect for the contractors and firms involved.