Warehouse Inventory Alert System

You are tasked with implementing a system that tracks the inventory levels of various items in a warehouse using a series of events. Each event is represented as a record with the following properties:

• timestamp: A value (integer or string) that represents the time the event occurred. You can assume events are given in chronological order, or you may sort them if needed.
• item_id: A string representing the unique identifier of the item.
• quantity_change: An integer that indicates the change in inventory. A positive number denotes an addition (delivery) and a negative number denotes a removal (shipment).

The system should process these events sequentially to maintain the current inventory for each item (initially, all inventory counts are zero). Additionally, whenever the inventory for an item falls strictly below a given threshold, an alert must be generated. An alert is a record (in your chosen structure, e.g., a dictionary) that contains at least the following:

• The timestamp when the inventory level fell below the threshold
• The item_id
• The updated inventory level

Your task is to write a function (or set of functions) that takes as input:

1. A list of event records (as described above).
2. An integer representing the inventory threshold.

The function should process the list of events and return a list of alert records in the order they were generated. Make sure your solution is capable of handling a large number of events efficiently.

Consider edge cases such as:

• Multiple events for the same item in a short period which might trigger alerts consecutively.
• Items that might never reach the threshold.

Good luck!