Answer:
The colleague has committed a violation because your customer's order could move the price of ABC stock
Step-by-step explanation:
Front running is also called tailgating. It is a prohibited practice where a trader enters into a position security based on non-public information about a large trade that will influence the price of the security.
The trade is initiated to take advantage of the new price that the large trade will cause. The position is entered before the large trade occurs.
In this scenario your neighbour heard you telling your client to but 100,000 share of ABC. Because the transaction will influence the market he also tells his client to buy 10,000.
This is tailgating and it is a violation.