Q. Do you think things happen to us for a reason (pre-destined) or is it based on karmic events?
A. This universe is a participatory universe, which means that what we perceive and know of it depends on the nature of the perceiving and knowing instrument. Just as tinted sunglasses reveal a tinted world, the configuration of mind determines what version and layers of the world we perceive. This is important because if we want to know the most complete answer to any question we ask, we must also include the condition of the questioning instrument in the answer. With this in mind, let's look at destiny and karma.
Another way we could ask the question about destiny, karma, and free will is to ask Do I have free will? Keeping in mind the first paragraph, it's important to note here that the question assumes the independent existence of the individual. In other words, the mind that asks this question is in the First Mind configuration. From the perspective of this First Mind, there is always the experience of free will. As an individual, I have a choice to stop typing now or continue typing. You have a choice to keep reading or stop reading. We may invoke many theories about how all effects are the result of prior causes and therefore there is no such thing as free will, but the fact remains that at the individual level of identity, the experience of free will remains.
Now a question may arise as to whether the experience of free will for the individual is the same as there actually being free will. How could we know this?
This is where the Second Mind - the deeper, broader, more comprehensive, and subtler mind - comes in. From the perspective of the Second Mind, the experience of free will in the First Mind is noted to arise from the creative impulses of the Second Mind. The entire universe is a series of impulses. You have may noticed that there is no such thing as inanimation in this universe. Everything is moving, even at the finest level of quantum fluctuations. This animation can be thought of as the greater will, which bubbles through the experience of First Mind individuality and expresses as free will. The creative impulses are themselves your own subtler will, but this you is a deeper you - you as the Second Mind.
Generally, the First Mind will fluctuate between the idea of free will and destiny as situations change. There is no final answer to be had in this mental configuration because the experience of individuality itself confers the experience of free will. The more complete answer is in recognizing the Second Mind configuration. When the notion of individuality is seen through (not ignored, simply seen through), the question of free will vs destiny starts to dissolve. This too is where the effects of karma are seen and their binding released. All effects are modifications of prior causes, and these effects themselves cause the next chain of events. This is karma in a nutshell. It does not mean there is no free will, simply that the understanding and experience of will changes when the mental configuration changes. The phrase "Thy will be done" is a First Mind speaking to the Second Mind. Both are you.
So, yes - there is free will, there is destiny, there is karma. And the understanding of these depends on which level of identity one is looking from.