LT Capital Gains - when to file

How does LT capital gains factor into determining if you need to file a tax return? My 20 year old, who is a college student and we claim as a dependent, will make approx $2k in earned income this year but will realize $2,500 in long term capital gains as a result of a sale of stock in his brokerage account. Will he need to file a tax return based on the above?