His mother died during his sophomore year, his father when he was a senior.
https://www.newyorker.com/magazine/2018/01/29/the-lost-giant-of-american-literature
His mother died during his sophomore year, his father when he was a senior.
https://www.newyorker.com/magazine/2018/01/29/the-lost-giant-of-american-literature
His mother died during his sophomore year, his father __ when he was a senior.
This is called a 'gapped coordination construction', i.e. one where the middle part of a non-initial coordinate can be omitted if it is recoverable from the corresponding part of the initial coordinate (called the antecedent).
The gap marked '__' is understood by reference to the first coordinate: in this case "died".
The fact that this qualifies as a gapped coordination construction by virtue of a missing verb (died) means that the second coordinate is not regarded as a run-on sentence.