You're supposed to call for a fair catch to preserve good field position. Northwestern's Miles Shuler called for a fair catch at the 3-yard line, which is not good field position:
Here are the potential things Shuler could've done:
1. Let the ball bounce. There's a very high chance the ball bounces 3 yards downfield after flying 50 in the air, so this probably would've been a touchback and given Northwestern the ball at the 20. You're risking that slim chance that the ball bounces perfectly and the coverage team and the coverage team grabs it in those 3 yards, but that's the only risk you're taking. This is probably worth 17 yards.
2. Run with the ball. Buddy! There's nobody there!
3. Take a fair catch, ensuring you preserve your opportunity to get the ball at the 3-yard line to prevent the opponent from pinning you at the 1 or 2.
Shuler opted for No. 3, the worst option by far. Of course, Shuler probably just lost track of where he was on the field, but when you're a punt returner, that's kind of an important thing to note.
This happened on the next play (ignore the "fourth-and-3" marking, it was first-and-10.)
Because Northwestern intentionally opted to take the ball at the 3-yard-line, they were only three yards from a safety, and sure enough, that happened!